She filled out an application for a payday loan which I am assuming was also her prom note. If she got the money, she obviously disclosed her bank account.
What state do you live in? How much was borrowed? When? How much is owed??
If the Payday lender has the license to operate in your state then your wife has to repay both the principal loan amount along with the interest. But if they're not then she needs to pay back the principal loan amount only.