Originally Posted by Blackcat31:
She submitted a deposit. That IS committing.
I love how parents view the deposit as a guarantee but ONLY if they want it to be that. Then when things don't work out on their end, it should suddenly be something completely different. 
E-mail her and ask her why she paid a deposit then?
When she replies "to hold the space"
Reply that you held up your end of the deal so the deposit is not refundable.
Yep!
I would have something written up to sign with your deposits in the future. But, your policies (which she received) state the deposit is non-refundable. If she took it to court (and I doubt she'd go that far), I doubt she'd win.