It's very typical. Kids go through "favorites" all the time, and it doesn't mean you're a bad mommy! It could be a reaction to the new baby but remember that your 2 year old is only a baby herself. It could also be a reaction to living with the inlaws and picking up some tension in the situation (you don't say how long you have been there but sometimes maybe she's worked at settling in there by connecting with Grandma. Also, kids pick up on their parents' stress, so if you're frustrating being crowded into temporary living quarters and worrying about your house getting ready, plus having a new baby, you're both probably kicking off some signals that a very intuitive kid can pick up on.
But, having other people who love her and help comfort her is great. In the long run, it's a good thing that a child can connect with someone else (a grandparent, an aunt, a daycare provider, etc.) - and when you live under the same roof, it's more pronounced. Kids need to learn to separate from the primary caregiver (when they don't, you'll see those parents here on Mamapedia complaining that they have velcro children who won't go to preschool or even let Mom take a shower!).
Finally, you might give some thought to your daughter learning to self-soothe. A lot of parents love co-sleeping and if you do and it's your choice, that's fine. However, kids who cannot learn to fall asleep by themselves and who need someone in the bed with them all the time sometimes miss the person who's not there. Your daughter falls asleep with Grandma, but then wakes up and is someplace else - that can be disconcerting. She thinks her sleeping place is with Grandma because that's where she snuggles up and drifts off to sleep. She's not aware that you are moving her into your own bed. You might want to think through how you plan to get her to sleep in her own bed, if not now, then in the new house. As part of this, you have to address your own feelings of having both children sleeping with you, and figure out how you will will transition. I'm sure a lot of people on mamapedia can recommend books on the subject.
Good luck - and I hope you can get some sleep!