Mother in law woes

My mother in law generally drives me crazy and recently she started watching our daughter a few days a week when I went back to work part time. She now keeps referring to our daughter as "our baby" or "my baby" and it's so stupid but it's driving me nuts! I know I have to pick my battles and I appreciate her helping us out during the week, but she does have boundary issues and I don't think that her believing this baby is "ours" helps.

Anyone else having mother in law issues after having your baby?