She has a link on her profile to a new AW facility where you can buy credit vouchers https://www.adultwork.com/Vouchers.asp She's called it 'deposits' but to be fair, this is perhaps a bit unfortunate as on her 'booking' tab she only asks for a booking request through the AW site and there is no mention of wanting a deposit.
If she asked she would get banned, adultwork have zero tolerance for people paying for prostitutes with their payment system, instant ban and loss of payments on both side.
That's why nobody mentions it on their profiles.
There may be nothing wrong.
The only other people that use the same feature are the pay piggy brigade again the sort I avoid.
Just checked my local top rated outcalls cannot see anyone else with this.
Up to her anyway, and she didn't ask you maybe reserved for those with zero feedback. I don't know or will ever find out really !