Because she is
Like everyone else said, it's her grandbaby and she obviously wants to be in his life. Besides saying she's mother in law is so much better than referring to you as her son's "baby mama".
She wishes you were married.
She is trying to let you know that you are always welcome in her life. She doesn't have a better term to use. She is trying to be endearing.
Classy. O.o I dont know. Maybe she knows something you dont.
Ditto the others - she wants to be in her grandbaby's life
that baby is her grandbaby. I'm sure she wishes she was your Mother in law...that you'd marry him. I hope she can have a relationship with the baby if she wants
Sounds like she's laying a claim to visitation with the baby