When you answer the question, "Who have you seen before" she'll cross reference reviews/mentions of those girls with those of hers and piece it together. It's a common question for that reason, but also to gauge what type of mileage you may have gotten in the past.
You can play the game too by naming random girls you haven't reviewed to throw her off the scent, but also you can give a hint to what type of mileage you are used to.
Heard Kourtney is amazing, but I find Platinum too grungy for my liking - have they fixed the drain in the shower in the back room yet?.
(Disclaimer: Maybe I've seen her but don't want her to know my online identity).