I wasn't really thinking of the prostitution charges when I read this, but the potential for getting popped by the local transportation department for operating w/o the locale's taxi/livery permits, insurance, etc if you're doing this for cash off-app.
Have you considered using something like Uzurv? The lady (and several civilians) could reserve your services at specific times; you'd show up at the scheduled time, the app would send the request to Uber or Lyft once you click arrive and the respective rideshare app would take over from there.
might be a *legal* way to do what you're doing, though you'd have to be careful in your communications to give yourself plausible deniability about who you're transporting. i.e. "I'm just transporting this young lady from A to B", not "I'm taking this sex worker to her client for an outcall".
I noticed your reviews are in the Waco/Killeen area. Do you normally drive in Austin? If so, you might want to get your local fingerprint/TNC card and sign up for FARE. That particular rideshare service has preferred driver lists and reservations built-in, and would be another good way for you to offer services to sex workers with some legal protection/plausible deniability.