She should have known that her mother, like you, has a stick up her ass about adults going out and having adult fun.
I know that when one or both of my parents, my friends parents, my relatives parents and everyone else's parents went out to eat, drink and be merry, they hired babysitters. That's a normal, ordinary thing to do, thousands of parents do it every day.
I know this is shocking to you, but adults don't turn in their grown-up badges when they have kids. They don't suddenly lose the stomach enzymes to digest anything but chicken fingers, Cheerios, and mashed bananas. Most parents will tell you that babies are not fun to be around 24/7, and that changing diapers is indeed a life-changing experience, and not in a positive way.
Their genitals don't fall off, either. I know a whole bunch of couples who will hire sitters so they can have evenings of uninterrupted nookie. Some of them do this so they can see their boy/girlfriends, too. That's what normal people do.
I remember clearly dinner parties at which all of the adults kicked us into bed after dinner and proceeded to play progressively louder card games throughout the evening. So does everyone else I know, and so do many people on the boards here.
If you sincerely believe that people with kids should never have a drink again, should never see their single friends again, should hide in the house and never leave unescorted, then I feel very sorry for you.
If you think that all married women should suddenly forget that they're human beings with human needs and a craving to have fun, then I feel sorry for your spouse.
What a boring little life you must have.