That ads gone, presume you mean this one:
External Link/Members OnlyCurrently called "The Domina".
The ad has come & gone on VS for a long time now. Seems to be at least 2 girls using it, one with tattoos, one without. It used to be just the one with tattoos, and a couple of years ago she also had a separate ad for vanilla escorting. Then it switched to just the one without tattoos for a while, now pictures of them both are on there.
I've also googled the phone number in the past & found ads for the tattooed girl on other sites as well, but they must have changed the number as the current one isn't getting any results.
As a final thought, and I've no hard evidence to back this thought up, but to me the picture where she has a finger over her mouth looks a lot like it could be stolen from DominaJemma in Bristol.
So to me, the longevity of the ad makes it unlikely to be a scam and is probably genuine, but the fact there are clearly two different girls using the ad makes it questionable what you'd get it you went for it.