Kinda sorta agree with you on that. Yeah, it's a 'deposit' not a gift. But given the nature of our little world it's not like you're going to report them to the BBB, drag her to small claims court, or call the police. Any money that one provides to the ladies prior to any services or time spent, is a gift. Label it whatever you like, you should have ZERO expectations of ever seeing that money again. Even if they say it's a loan or they promise to provide time and services later....you ain't seeing that money again. It's all a gift until after the fact.
And to the OP: Sending over a $500 'deposit' was not a very elite move on your part. Never send a deposit. Even if you think you know the lady really well. Never send a deposit.