that explicitly state they are full service?

I'd say this lady's ad and site are no more ambiguous than some of the well known providers in the area.

Discrete is the only safe way and I would advise not even asking beforehand.  Someone's gotta TOFTT.  Too damn hot looking not to check it out.   I would definitely insist on proof of age though.  Pretty sophisticated ads and web-site for that age - must be someone behind the scenes helping her - pimp or agency.