What would you do if your MIL kept telling people about your pregnancy?

Sophie 💙

So I'm 5 weeks 4 days pregnant and obviously so excited. I told my parents and sister practically hours after we found out because they are the most secretive people ever and haven't told a soul. We told my MIL on Monday, at 5 weeks because stupidly, thought she wouldn't tell anyone. She's told her 3 other kids, her fiance, her sister, her mum, her sisters partner and children (and their partners), her colleagues, her friends, etc etc. I only wanted parents to know and my sister purely because my family is literally just me, my parents and sister. So I couldn't tell either of them without telling the other. However, my partners family is massive and it's too early to tell everyone. And also, it's our news to tell, not hers. Especially as it is our first baby. What would you do?