Oh, I didn't mean that he should walk up to her like he knew her but not say from where.  Definitely that's creepy.  Although when one works in public with lots of people, we get sort of used to dealing with that, right?  People come up to me and start chatting all the time and I am desperately trying to figure out where they know me from so I can respond appropriately.  Mostly I just smile and nod and hope a clue comes out of their mouth soon.  Sometimes -- and this is the most hilarious -- I realize that the other person is in the same boat.  Neither of us really have a clue how we know each other, but are just trying to be polite.  But young women are the toughest.  I remember everyone I've hired, of course, but I know more working women than that and lots of people know me (especially in Europe), so some woman will say hi to me and I am thinking 'Uh, OK, is this a medical student or a hooker...?'  In Europe the English skills usually give it away fast.  But not always.  There was this one girl and I was convinced she was a researcher, and I'm like 'So how're things, blah blah',  And she's like 'It's been good, actually, really busy.'  And I can't even remember what her project might be, so I'm like 'Well, busy is always good...' And she's like 'Yea I guess so but I need some sleep' and I'm like 'Oh well the holidays are coming up' and she's 'No the holidays are always really busy!  By the time it's Christmas I can barely walk!'.  And I'm like...  Uh... OK.  

Anyway, I meant to say to the OP that he should treat her as if he had never seen her ad at all.  In other words, just treat her like any other person he might meet in the gym and want to meet. Her job is irrelevant and the fact that he's a John is a turn off.

I met my wife (who was a provider that exact same way).  Just pretend like you know nothing about what she does and move forward like a normal woman you would ask out on a date.  It's really pretty simple.