There is no anonymous way of sending a secure, returnable deposit. Sending a picture of a card does not confirm that it is valid, she has to redeem it, and hence cannot return it.
I guess you could courier cash to the lady in advance.
I don't think I'd ever be in the market for a visit to a lady that requires a deposit personally. Either they'd be too "high end" for my needs, or too sketchy to risk a deposit.
One thing I think most reputable providers would take into consideration is whether you have a credible presence on a review board like this one. I can see them making an exception for a long time member here, especially one with many fair reviews. Much as we want to know an SP is real and reliable, they want the same. I still remember booking a visit with a lady who was a local, but had moved and returned occasionally. She checked my PERB reviews and was hesitant to book because I had mentioned in a review that the SP was not as toned as claimed, and she worried that I might leave a negative review of her because while she had an awesome body, she had a little tummy. I laughed when she told me, but was amazed that she did that deep a dive on my presence here.
Newbies looking at unknown SP's wanting a deposit is Russian Roulette, and I wish you luck. If I was in that space, I'd stick to the well reviewed, safe options.