Too many red flags on that one for me. Low price, high deposit. I have paid deposits in the past but only for well-reviewed girls on AW and when I a booking days in advance. I can understand the girl wanting to be sure that clients will show up for advance bookings. If you are chatting with her, when you are available, I would message and say that I can be there in 20 minutes. If she is free, she is not losing another client before you get there.