How to deal with asking MIL not to tell people when I go into labor?

Natasha
I'm 32 weeks pregnant and I've decided that when I go into labor that I don't want people to know except a few really close people so I can do a really cute announcement. The main problem here is that my future MIL tends to not be able to keep her mouth shut and has essentially invited herself to the hospital and into the room. Also, her brother is an oversharer on Facebook. When I found out I was pregnant I was 4 weeks along and after having an ectopic pregnancy last year, we asked her not to tell anyone because it was so early and we wanted to wait. Within three hours her ENTIRE family knew. I know she's excited to be a grandma, but I feel like with my child, my wishes should be followed. I don't want anyone at the hospital except my boyfriend and my best friend, especially in my room, but I'd prefer everyone to wait at home and give us our time to be parents before everyone starts rushing to see the baby.