My mother in law ruins everything

My last pregnancy, we let my mother in law in on all of the news before everyone because we thought it would be nice. Well she told people when she wasn’t supposed to so this time around, she’s waiting to find out everything when everyone else does.

We know the sex of the baby but haven’t told everyone. My mother in law insists that this child is a girl and keeps calling the baby “she” and “her”

The baby is a girl and my blood is just boiling for the day we tell everyone and she decides to say “I told you so”

I don’t know why she can’t just wait until we announce and be normal. What if the baby was a boy? She really just needs to stop and be patient. Ugh