Second to last letter. This kids, is why you don't make major life decisions based on what OTHER PEOPLE think is going to be best for you.
It's one of my secret dreams to become an advice columnist and end every answer with "don't be a dumbass."
MIL in the article is no doubt a manipulative "B" but letter writer is extremely dumb to intentionally make that kind of a decision(s) based off a "promise." If you're not confident enough in yourself to stand your ground in something as important as bringing a child into the world, what kind of example does that set for a child?