I wouldn’t cosign any loan I couldn’t afford to pay back if the situation arose; it wouldn’t matter where it was from. Unexpected things happen. When you cosign a loan, you’re saying that if something does happen and the student can’t pay, then you can and will. I would never sign a paper saying that I can when the reality is that I can’t.
Did the student say whether or not they have siblings? As a parent, I couldn’t cosign a note for that amount for one child unless I was able to do that for all of them. It’s not unreasonable for a parent to tell a grown child what they can afford to risk and expect the child to take it like an adult. Complaining to Dear Abby isn’t taking the news like an adult.