As usual, there is often another shoe (or two or three) to drop after the first message.
Q1)"How much could I expect to get if sued?"
A1)I assume you mean how much can you sue for. If so, you can sue in Small Claims for your actual losses only.
Q2) Should I add interest to make it more worth my while?
A2) If this were a loan with a contract and interest, you would be able to include the 'pre-judgment' interest. Without any specific interest rate in the agreement, you can't get it. However, your judgment will be awarded post-judgment interest until paid.
Q3) "What if I don't know her Az home address?"
A3) This could be a 'sticky wicket'. You will need her address in order to serve her with notice of the lawsuit. You can get her address from private investigators, reverse phone lists, etc.