I'm not going to let my mil watch our newborn baby
Is there a plan already for if she just shows up?
I'll lock the doors and I won't give her a key. And I am going to see my mum's reaction.
The mother in law has a right to watch the newborn baby. You shouldn't be rude to your mother in law like that. She is there to help and trust me,  you will need her help with the baby one day.
Me? Rude? My mother in law is a rapey bitchie cunt.
I think that you should be a little more respectful to your MIL. It is going to effect you in the long run if you are rude to your SO's parents.