Starting out with Proton Mail as an email do not think she is a complete rookie/
At least has a local area code for phone .
That being said send her 50% deposit and tell us all about this hot number. Must be using hotel with higher Incall then out rate.

She may be new, and having the help of someone who  has a slight idea of how this works but did you read her Cancellation policy?

"Your deposit is not refundable in event of cancellation."

It doesn't break it down and say "your" cancelation, its states A cancelation.

Now myself, personally, in my decades of doing this, have never paid a deposit, and I never will, but you get to make your own decision.

That being said, she is attractive, but not exceptional, to me,  and I wouldn't pay her rates.

You did ask for my ideas, and there they are, you make your own decision and cost/benefit analysis and I wish you good luck.