Ash,

There is a concept called “boundaries”  This is where you are clear on what is acceptable and not acceptable behavior with others.  Once you know that for yourself, clearly communicate that.  You also need to be willing to take action if someone crosses those boundaries; whether it is walking away, cutting off contact, being strong and direct in calling out the unacceptable behavior, etc.

You may want to have a “plan of action” whenever you deal with your mother on such topics of marriage and children.

Mark