Pay her a compliment back - "You're so pretty. I bet loads of guys ask you for extras? I'd be v tempted - as you as so hot"
Exactly this - just use a bit of nuance.
If you say something like this in a fun way, you'll get things understood without damaging the relationship or embarrassing her or yourself....
The averages are around a third of blokes who call for first appointment will ask her upfront - so she won't be shocked by the question.
She may say "they are all dirty perverts" or some-such but that's not you!
On many occasions over the years I've had dinner with a legit therapist I've got to know.
I don't understand the aversion to that idea higher up the thread.