I have a 2-year-old granddaughter who is so attached to me she will resist her mother, sometimes very strongly. My concern is my daughter's feelings. She already feels guilty enough for working. I kept this grandchild at home for the first 6 months of her life to avoid early daycare. At first I thought it would be a passing thing but it seems to be getting stronger. I don't live close so I visit about every 2-3 weeks for a couple of days. When I'm not there, things are fine. Is this normal? Could it be that I am more relaxed and have the time to play with her that is driving this? This really seems more intense than I remember with my own kids.
That sounds entirely normal to me. Some part of that is because you had her for the first six months; she has very good memories and feels safe with you. That's a good thing!
However, it's normal even without that. My oldest loves his grandma and is regularly talking about how he'd like to go see his grandma (who lives 6-7 hours away) regularly. When she does visit (about as often as you do), he wants to spend the whole time with her (and is a annoyed when she spends a day with his younger brother). She never spent a long time with him as a baby - she was here for the first few weeks, but nothing like what you describe.
The concern is how to deal with her resisting her mother. You don't specify detail on what this entails, but I imagine at minimum she resists going back to her mother - ie, you take her for a day, then at night come home and have dinner with mommy and then it's time for you to go, she either resists going back for dinner or she complains about you going.
The first thing is that your daughter/her mother should understand what's causing this: it will happen no matter how well she parents or how she treats her daughter. The resisting is not related to her in any way: your granddaughter wants to play with grandma because it's fun to play with grandma. It's also a transition; transitions are hard for children at that age no matter what the conditions. She's having fun playing with grandma, she won't want to stop until it's not fun anymore. This won't help entirely - it's hard not to take things like this personally - but if your daughter remembers that, it may be of some use.
Secondly, you can help her with the transitions. Give her more information about exactly when things are happening. Use a timer to indicate when you're going to leave or when she's going to go back to her mom; tell her "I'm leaving in about an hour", then remind her again at half hour, fifteen minutes, five minutes, and one minute. She will both expend some of her resistance then, and will be mentally prepared for your leaving. It won't entirely eliminate it, but it often helps.
You also need to make sure she knows when you're coming back. It's hard as a child to believe that this isn't the last time you'll ever see someone every time they leave, because children of that age have weak senses of time. You can help this by giving her a schedule of when you're coming back. "I'm going to leave now, but I will be back in three weeks."
Of course, she doesn't know what a week is, so you need to help her there - give her a reference point, like "Count trash truck days with mommy three times, and when the third one comes, I'll be there the next day," or "You'll go to church two times and after that I'll be there a few days afterwards. " Whatever is a weekly occurrence that is significant in her life and she can count (if she can count, if she can't then Mommy can help with this).
Also consider a calendar; write on the calendar the day that you are coming, and have her and Mommy put stickers on the calendar once every morning or evening at a consistent time to mark the day passing, and Mommy can show when Grandma is coming next. Then, when you come to leave, you can point the calendar to the next time you're coming, and remind her she can do this fun activity (putting stickers on the calendar) until you come again. (You'll have to do something slightly different if you don't have such a good idea of when you're coming next, of course.)
Ultimately, having a good sense of understanding and control will help her a lot. Nothing will work perfectly; my son complains every time he has to leave Grandma. But it's short, and we talk about when she's coming next, and he then tells us what he wants to do with her the next time she comes. (We didn't have to resort to the calendar, but we thought about it.)