Agh! MOTHER IN LAW

Okay my baby boy is here in 2 months ... long story short she thinks its her baby !!!! I can't take it anymore , she wants to choose the name , and do her own baby room at her house , she really thinks its her baby !! If we say something she will say " its my child , and I don't agree " And don't let me het started on the baby shower !! She wants everything she likes , my own mother doesn't even have a say in anything because she does every thing on her own !!

Any advice ?? Please because when MY baby is here , she is going to take over and tell me what to do.