Overstepping mother in law😬. What would you do?

So I’m 18 & 36 weeks pregnant. I live with my boyfriend and his mother. His mom has been so supportive and helpful and I’m extremely grateful for that. But she is also overstepping. She just assumed she was going to be in the delivery room without even asking me. I have never mentioned her being in there once. Then she went out and bought matching robes for me and her to wear in the hospital and I asked why she was gonna wear one & she said so she could do skin to skin contact when the baby is born. I never said she could do that either. Like I just wanted that to be for me and my boyfriend... and last night my boyfriend was telling us that he has to get a waiver signed saying who is going to be taking care of the baby while he is away in the Air Force and his mom said “oh yeah just get the waiver and I’ll sign it”. Like I’m 18 years old & this is my baby.. so why would she sign the waiver? I will be with the baby 24/7. He is mine. Not hers. That really pissed me off. I understand she’s excited and I’m very thankful for all she has done for me and the baby but I’m actually dreading him being born because I know it’ll be 10 times worse.. I’m very uncomfortable and I keep crying because I’m very capable of taking care of a child. I know I will need help, I know I will need her advice, but this is my son and I want to experience every part of motherhood myself. Good and bad. Without someone constantly stepping in and acting like his mother. How should I talk to her about this? I’m not a confrontational person and I tend to let people just walk all over me so this is going to be so so hard but I just really need advice on how to go about this in a nice, but firm way so she understands. Please help!