I side with FB on this one. I've looked at that ad many times and I think it's a "generic" ad for other girls that are working from Kai's flat in Rochford. I used to see Kai quite a lot in the past when she worked from her flat just off Southend seafront. She can be very hit and miss at times, but overall I used to like seeing her for a rubdown and a quick fuck.
Best thing to do is phone Kai on her ad and ask if her "sister" is with her. I saw a few other girls at her place (who she always referred to as her "sister") and had more of a full on experience with them than I did with Kai. So if she has someone with her, opt them instead.
Happy humping!