The schedule sounds OK, although it's more sleep than my son would have managed at that age, I know that some children do sleep more. The problem seems to me like a combination of not being quite tired enough at bedtime and possibly too many negative associations with her crib and bedtime.
I think this can be a tricky age as it's around the time that many children start to transition towards one nap but are not quite ready for it yet. The fact that it takes so long for her to fall asleep, whatever you do, really sounds to me that she needs a bit more time awake before bedtime.
At this point you might expect bedtime to get a bit later. So as a first step, I would suggest starting the bedtime routine a little later so that she can still fall asleep at a similar time but without it taking so long and causing so much stress to all of you. Another thing you could try is pushing the naps a bit later and cutting the second one a bit shorter. She should eventually, as she gets older, transition to one later, longer nap.
However, the fact that you've said this is not a new thing and has been going on for several months, suggests that she is feeling badly about her crib and bedtime. This could be from trying to get her to sleep when she's not ready to or it could be something else worrying her. It's almost impossible to know at this age as the communication is limited. But what you could try is doing something as part of her bedtime routine where she's doing something enjoyable but restful in the crib that's not trying to fall asleep. This could also help in the process of getting her to fall asleep alone and without breastfeeding. We started this process with our son by making sure he stayed awake for his bedtime feed and then my husband or I reading some books while our son sat in the cot. You could also try to tempt her in with a few of her favourite cuddly toys. After a while of starting this our son would lay down by himself when he got really sleepy.
Although your question title is about how to get your daughter to fall asleep alone, the question itself sounds more like you are just looking for a way to get her to fall asleep a bit quicker without so much upset so I've mainly focused on that. However for the bit about falling asleep alone, you could see my answer to this question:
How do you get your kid to lay in the crib?
As I mentioned in that answer, there are various methods which involve letting your child cry for certain periods but we've tried to avoid that so I can't really offer any advice on it but I think there are plenty of places on the internet with lots of details. I've given more details on a gentler option in my other answer.
We are now a bit further on from that answer. Our son is now 2 and still likes one of us to be in the room when he goes to sleep but he recently stopped wanting us to pat his back or try to help him sleep. This particular step happened without any effort on our part so it seems it was just a natural progression as he developed. As the accepted answer to the question that Ida linked suggested, children should naturally start to sleep with less adult interaction as they get older. Our son's sleep is still not perfect but it has improved a lot and we're now starting to realise how quickly the time passes and he needs us less as time goes on. Now we're feeling that we want him to stay small a bit longer.