Legal Question in Credit and Debt Law in New York

This should have been done before you gave her the $. Do you have any written proof of the loan?

The type of agreement you describe should've been prepared and signed before you gave your friend the money. Even if you could have convinced your friend to sign off on that type of agreement, it wouldn't have been binding on the lender because you are not in "privity of contract" with the lender. As a practical matter, a big commercial lender wouldn't want anything to do with a small, personal agreement between you and you friend. The situation would be similar to having your friend ask a McDonalds cashier to cut your Big Mac in half and to deliver it to you at your table.