If she couldn't make the original payments, what makes you think she will with a 300% interest rate lobbed on top? She would be better to close the account and negotiate a repayment schedule that will save her that interst in the long run.
A bigger bandage is not the solution here. If she has already defaulted on the original contract the credit is already down the pike so to speak.
Robbing Peter to pay off Paul will only leave you with.