Overbearing MIL

My husband has a 5 year old daughter from a previous relationship and when she was born my MIL all but destroyed my husbands confidence in raising his child. He got 50/50 custody when she was 6 months old and his mom would constantly plant seeds of doubt so that he would need her help. She would say “what if you dont hear her on the baby monitor and you dont wake up” or she would talk about SIDS and just so much shit to scare him. He started spending the night at his parents when it was his nights with her. They had their own nursery for her and would go tend to her in the middle of the night and not even try to wake him up. I put a stop to that when we started dating and helped him know that men are perfectly capable of doing this! Now i am 18 weeks pregnant and my MIL is mentioning how shes ready to help overnight with the baby and she really thinks she is going to get to keep my baby overnight all the time. I feel like There is going to be a big fight and i am going to be hormonal but im letting her live in her dream world right now. My baby is not staying the night away from me for at least his first year!

Thanks for letting me rant hahaha