UPDATE:

I sent her an email and waited a few days for a response, and I still didn't receive anything.

We decided that instead of giving you a free cake, I would do it for 50%. I figured she would pay at least for the materials and I would donate my time. Of course, with the condition that she paid her remaining balance.

Thanks to everyone who gave me such wonderful ideas. After much discussion, I felt that this was a fair route for both of us.