“Does my son have to pay me back for his extra time in college?”’
This is odd wording when you look at it. I think most parents know that particular answer because nobody HAS to do anything. You can sue relatives and friends but it’s never good.
So let’s turn it into the flip side of the coin… “Do I have to pay my mom back for my extra time in college?”
If this was the kid asking, I’d say yes if you want any respect at all. You need to step up and pay it back because that’s what the agreement was. Try to pay it back but three years is pretty tough terms for a new graduate (depending on salary). If unable to pay it back except in smaller increments, I’d try to negotiate some terms with “bank of mom” who has already given generous interest rates (probably zero). Come up with a payment plan. Get Dave Ramsey’s “Total Money Makeover” and make a budget pronto. Grow-up. Both son and GF will be happier debt-free.