I'm not sure if this is just a phase, or if you're in actual danger of losing your daughter - it would depend heavily on how she'd describe things, I suspect.

There is, however, one detail which makes me worry:

"you are just giving me more courage to leave you to die alone"

That sentiment sounds a lot like a sentiment I would have thought to myself (though wouldn't have had the courage to say) - and after things failed to change, I did end up cutting my mother out of my life. I would be especially worried if your daughter sounded calm while saying that; if she sounded aggressive or emotional, then perhaps it was just a verbal barb in the heat of the moment.

Other answers have addressed the "it'll get better in time" possibility, so I'll instead provide some context on why I'm estranged from my mother, and how she might have avoided that.

First of all, the first paragraph you give doesn't sound overly concerning. That seems potentially normal, or at least not alarming - physical touches from your family is weird at that age! It's the more recent description that sounds a bit off to me, and potentially worrying.

In terms of how things progressed with me, things got shaky in my early teens (once I was old enough to start standing up for myself, basically), at about age 16 I remember distinct cases where we snapped at each other in public or in front of community figures I respected, and by around 19 I had essentially given up on having any real relationship with her, and was biding my time until transferring from junior college to a university with dorms.

If your daughter is having a similar sort of hardship in her relationship with you, then it's not necessarily too late yet - but in that scenario you wouldn't want to just "tough it out", because if things get too bad, then later on, it might be.

So, how to fix that sort of situation?

In my case, there was at least one recurring issue that forced a wedge between us, and I think my mom still doesn't comprehend what it is. In cases like mine, it's imperative to address the underlying issue rather than the superficial fighting, otherwise I would expect a begrudging relationship at best, or no daughter at worst.

Interestingly, my mother and grandmother had the same sort of friction in their relationship, and with a similar cause. My mother was clearly never happy when she "had to" interact with my grandmother. That's part of what gave me the courage to avoid contact with her (why, in the modern world, should I do the same thing as her when it had clearly only caused her pain?), and why I mention the possibility of a begrudging relationship (which is not a good thing, in my opinion).

Perhaps counter-intuitively, trying to cling to your relationship with your daughter is unlikely to help in this scenario, because she might chafe at the forced interaction. Similarly, reminiscing about how good things used to be won't necessarily help. That might seem like senseless nostalgia to your daughter; in my case, it actually felt like rubbing salt in the wound, once things had progressed too far. At 16, I might have lashed out and maybe had a painful-but-productive argument, or maybe decided that my mom was out of touch; at 19, it was just depressing hearing my mom talk about that.

Something that would have helped, in my case, is some manner of counseling or therapy, preferably with someone who could build a good rapport with me as well as my mother.

Another thing that might help is having an honest, heart-to-heart talk with your daughter. This might be tricky, however. For one, you'd need to accept the possibility that it might be painful, and that she might vent at you (at this age, it would be important to be the calm, mature one; when I had to shoulder the burden of maturity in fights while still legally under her care, that was one of the things that drove me away from my mother). For another, you would need to be ready to listen, even if it hurts - and you'd also need her to believe that you will listen. This is part of why I suggest a counselor, to help facilitate productive discussion rather than just another fight.

It may also be useful to give her some space, while still welcoming her in your home. Let her live her own life, but as a welcomed part of your family. At the very least, this would have helped in my case to keep things from deteriorating further; and if things aren't so bad between you and her, it might get her to open up when she otherwise wouldn't have. As an example, if you're having an argument that doesn't need to be resolved then-and-there (e.g., not a fire hazard or anything), and she walks off to sulk in her room? Good, she's safe under your roof, and also more likely to calm down if she has some space to herself. If she wants comfort later, then offer it; if she just wants to be left alone, then don't pressure her.

I do hope that things work out in the end with you and your daughter, preferably without too much stress involved. But if this is more than "just a phase", then hopefully there will be useful knowledge to take from my experiences.

Rewritten based on the edited question, which has an important elaboration on the scenario:

Yes, this sounds to me like your daughter might not stay in your life if things don't change. However, it seems like the main issue isn't necessarily with you - so you might be able to salvage your own relationship with your daughter (maybe not your brother's / her uncle's), though perhaps not in the form that you would like.

Now, for context, I'm estranged from my mother, and this has impacted my relationship with my dad and sister (it's a lot harder to see them, after all, given that I'm trying to avoid my mother and they still live with/near her). A few specific details make me think that your daughter is likely to do something similar once she's independent, if things don't change.

I can remember what she said when we saw each other after the fight: "you are just giving me more courage to leave you to die alone".

This sounds very blunt, and also shocking. It also sounds fairly similar to things that went through my head once things had gotten really bad between my mom and me - however, I never actually said anything of that sort, because I was afraid to. In my case, sentiments like this only really started popping into my head after I had given up on having a relationship with my mom, which given the context, sounds like a bad sign for you. However, the fact that she had the courage to say it to you makes me think that she at least respects you enough to offer a warning - unless she was just trying to get you angry, and without knowing how it was delivered, I can't say whether or not that's the case.

Her boyfriend also told us she said she doesn't feel her family as family, that she feels disconnected.

This also sounds familiar, although I phrase it slightly differently. I don't know how it is in your culture (her generation's version of your culture, as well), but in mine, this is a significant step towards considering words like "kin" to refer mostly to trustworthy friends, rather than blood relatives. So yes, given the strife, this seems like another red flag that your daughter might not stay in your life.

A related sign to watch out for: does she feel like your house isn't truly a home that she can return to and be comfortable in? If she doesn't, then she's less likely to go back there when times are tough, when holidays roll around, and the like. Especially if she actually felt unsafe, or perpetually uncomfortable.

Which brings me to the last thing that makes me worry in this case, although there's not a succinct quote: when your daughter fought with your brother, she ended up being told to leave the house. At the very least, that would have been a significant shock to her. The way you describe it also makes me think that she might end up trying to cut him out of her life when she's older, and if I may be blunt in describing the child's point of view, keeping contact with people we're estranged with is a lot easier when they've been important in the past.

So, what can you do?

I would recommend attending family counseling and making sure that she feels safe, comfortable and welcomed in your house, as the first things to do. If she doesn't feel like your house is safe, and a home for her, then based on my experience I'd say she's a lot more likely to drift away; and there may be various issues she's dealing with, which would be more appropriate to treat with counseling than with advice from the internet.

It also seems important to talk with your daughter about the issues she's having with your brother, and/or any other similar issues. I expect that your daughter knows there's a lot of tension between the two of them, and also knows that you're aware of it. If you discuss it with her, and really listen to her (even if you don't necessarily agree, but do listen and don't try to deny her feelings), then the fact that you've done so may end up being very important to her. This worked rather well for my dad, who helped mediate between me and my mother when we fought - and I do still look forward to our sporadic catch-ups, when she's not involved. He helped me keep my sanity, after all, even if he was rarely (if ever) able to actually stop the fights.

If you're able to, it could also be good to offer her some safe space of her own in your house - a bit of autonomy, but still under your roof where you know where she is (and can welcome her as needed). Nothing you've described so far makes it sound like her primary problem is with you, so giving her a bit of freedom while she's under your roof could go a long way towards making sure the relationship between you and her stays good. This is not to say lawlessness or anything, of course, but more the ability to just relax, so that she doesn't have to constantly be on edge worrying about family strife.

Other than that, giving her reasons to come back might also help. However, in my judgement at least, making sure that she feels like she's venturing forth from home rather than getting away from strife is the far more important part.

Other answers have addressed the "it'll get better in time" possibility, so I'll instead provide some context on why I'm estranged from my mother, and how she might have avoided that.

Other answers have addressed the "it'll get better in time" possibility, so I'll instead provide some context on why I'm estranged from my mother, and how she might have avoided that.