Am I being unreasonable with my pregnant daughter?

[Jessi1972]

Hi everyone, this is my first posting and I apologize if it's long winded it here goes.
My daughter is 23, and generally funny and full of giggles and I love her so much but right now I'm scared of losing her because she's pregnant and her boyfriends "mam" ( not his real mother, she got him after her sister passed away) and before you ask, yes I do admire her for doing that but I don't a admire her for the way she treats people including my daughter's boyfriend, my daughter, myself and the rest of my family.
Yes, she's had a mental breakdown, she's extremely controlling and she feels she is the boss and takes over everything and everyone.
A little back story is her "daughter" is nearly 30, had a baby 2 years ago, currently has nothing to do with her child, stays in her room all day everyday watching Netflix and eating McDonald's and this is because when the baby was born "mam" took over and we now have a very confused 2 year old and an extremely depressed 30 year old.
My daughter has been dating her boyfriend and because of pressure from "mam" they are now pregnant - I should say at this point I'm excited about becoming a grandmother and don't have any problems with her being pregnant and living at home - I work and can support her and the baby.
"Mam" won't let them get a place together as she thinks her son is irresponsible (she won't even let him control his own finances) and yes I hear you screaming RED FLAG! THE FLAG! RED FLAG!
This "mam" is now taking over, booking appointments, telling my daughter what she can and can't do being pregnant, making arrangements without consulting or consideration to us or anyone else and the icing on the cake is that when my daughter and baby come home she has informed us that she will just walk in our house and take the baby! On hearing this my partner went ballistic and is now changing the lock on the door so it will be permanently locked.
This situation has upset myself, my other daughter and my partner all in the space of about 10 days of her finding out about the pregnancy!
If this is what's happened in 10 days, imagine what the next 8 months and beyond are going to be like!
I also understand when you all start shouting "so tell daughter it's your house, your rules and if she don't like it tell her to move out" but I'm her mother. This will be my first grandchild and I don't want to loose them - yes I'm scared! so please, any advice would be grateful
Thank you for bearing with me while I rant, maybe I'm overreacting, I don't know?

[lifeinthedeep]

Isn’t his baby more important than the two dogs? At 23 they need to grow up and should be looking to find their own place or risk having to live by other people’s rules. Does he work? Can he support her? It’s going to be a very confusing dynamic if they live apart.

I’m not judging, I’m a young mum myself at 21. Living with my parents/ the in laws while pregnant was hell in terms of interference. Mam sounds like a nightmare that they need to move away from. While he’s living with her the majority of the time she is a major threat.