B.M.
Hi K.,
This could stem from the idea that your daughter just lost her home (in her view) and now has to live with Memaw. Her anger over the move is being placed on Memaw. Perhaps she sees this as Memaw's fault. Sit her down calmly and kindly and talk about this with her. Don't ask her about it, because at 3 she probably doesn't even know what the problem is either. Try, "I know it was hard to move, and Daddy and I miss our house too. Memaw is being very nice letting us stay here and soon we will have our own house again, with our own stuff. Until then we are all going to be extra nice to Memaw for everything she does for us." You could also try rephrasing her statements for her when she does say something mean. "How can we answer Memaw in a nice way?" or "The right thing to say is Hello Memaw." Give her some support in that area, but be absolute with your expectations.
I hope you find something that will help your little one feel better.
Take care,
B.