Believe me, I feel for her situation - and I agree that his refusal to pay his loans and leaving her holding the bag for them is just one more sinister layer to his abuse. Unfortunately, this aspect isn't legally relevent to the situation at hand.

Sallie Mae would have to be willing to let her out and make modifications to the original loan agreement. If she's been the one making the payments, that's not likely to happen. They want to keep whoever is going to pay it on the hook. If the ex had been making on-time payments for 24 consecutive months, they might have worked with her, but they're not about to let the only one willing to pay get away. They made a loan, and they are due repayment - they did nothing wrong, so no reason for THEM to be out the money. I know that sounds harsh, but from a legal, non-emotional stance, that's the cold hard truth and God-forbid if they ever have to begin collection proceedings, they'll win and will come after the assets of whoever they can reach (which might include YOU if you have assets co-mingled with her like in a joint checking account).

One thing she might want to look into is getting a free consultation with a few bankruptcy attorneys in your area. While student loans generally can't be included anymore, it's possible that if the loan goes into default, and she declares bankruptcy, that the full burden of the loan would shift back to him. So if she's prepared to take the credit report hit for a while, to save the monthly payments, this might be a strategy to consider (obviously BEFORE you two get married, if that's the plan).

For the benefit of others reading this post: DO NOT EVER COSIGN A LOAN LIKE THIS FOR A BOY/GIRLFRIEND!!! Marriage has the benefit of the divorce process where a court can separate debts and assign liability for those debts. Acting like you are married financially without being married legally can result in DIRE circumstances!