Im pregnant & my mother in law is overbearing?

im pregnant with my 2nd kid and my mother in law wants to do everything as if she were the mother. i hav a boy and i recently found out i as having a girl since she has no daughters or granddaughters she want to take over everything! since this is my 1st daughter i want to be able to do the things to get prepared for the arrival of my baby. you see i give her an inch an she takes a mile. i don't want to hurt her feelings but how else do i tell her to back off a little (my boyfriend is such a Mommy's boy so it will cause arguments between us which ii do not want)