A well known tactic indeed that expands their market to blokes who wouldn't otherwise punt.
I don't see much difference between this and any other standard un-reviewed "escort" ad, provided you haven't already exchanged any pics or contact details, while still under the impression "she" wasn't a hooker, that they could potentially use against you in the very unlikely event it's some kind of more malicious bribery scam. In this case though, and you've subsequently shown interest in the punt, they probably already have all the ammo they need.
Likely worst case scenario though, it's some fat, ugly, old gypo squeezing into a pair fishnets. The likelihood of this though could be somewhat determined by the prices. What are they?
Just be prepared to walk if it all goes tits up, or through the floor if that's what actually answers the door.