and Talk to her , ask her how she feels and get her involved helping with Baby .
Sounds like she is feeling left out ,its a lot of stress for a 7 year old, a new Baby ,a new house with relatives , she probably sees everyone giving her new sibling a lot of attention, so make sure she gets attention and one to one games from you, if theres a Dad around get him involved aswell.Ask the relatives to do the same , she has lost a bit of self esteem help her get it back.
Did you used to post under a different name? I don't see where you've "said it before" that this behavior isn't every day or constant.
It sounds like, since she hates living there and there have been so many changes, that she needs her own private room where she can be alone when she needs to be, and no one else shares that space unless she invites them in.
Is that possible? How soon can you move out from this bad situation?