Legal Question in Credit and Debt Law in Indiana

As far as your obligation to repay the student loans that you co-signed, I doubt if you have any legal recourse. The loan company is entitled to go after either one or both of the co-signers, and your mistake concerning the nature of the relationship is irrelevant to the loan company. You do have a valid claim against your ex-fiance for contribution. I hope for your sake the amount involved is less than the small claims court jurisdictional limit, so you can file a claim for relief yourself. But if you do that, she will be able to bring forward all the good things she did for you, that it was actually a partnership which you abused. Maybe the best you can do is imagine how happy you are that you never actually married this person. Good luck.