The profile for a reviewed lady includes a section for DATY (yes or No).  This will tell you whether she allows guys to go down-under.

and many providers feel that they haven't done their job if you don't get off.

I suppose you can discuss it.  There may be some gals who would look forward to it.

Check the ladies profile here on TER. Lick pussy is indicated. It will say Yes, No, or Don't know. Read the juicy details (You need to get VIP status see the profile answers and read the juicy details. It's worth the money). I can't remember reading a review where DATY didn't take place. I have dined at the Y in every session I have ever had. I've heard that some ladies don't offer that but I've never seen one or read the review of one. I expect it if she says she is GFE. Best way to broach the subject is to ask/suggest it at the point you want to do it.
You could PM reviewers that have seen the lady but they may not be comfortable sharing those details with you if you don't have any reviews and you will need VIP to be able to send and receive PM's.

Comes down to  - Get VIP then all the info will be available to you.

to try and get an idea of services before coming out and asking her. If you still feel the need to ask her, you may want to approach that carefully AFTER you have been fully screened and o.k.'d for the appointment. However, there is potential you could be rejected for your appointment. It just depends on the provider.

Also, if after all of your research, you have gotten the feeling that DATY is offered in the session, it never hurts for you to make the first move in that direction and mention your likes - you should get guidance from the lady if you are absolutely not to go down there

Have fun and play safe

Summer

So you can see if this is something she allows.  If so, after she has provided you with some pleasure, simply say you want to reciprocate.  Pretty easy.