I find it funny how just about every girl on AW claims to be bisexual and says they will meet women as well as men.
Do you think lesbian / bisexual women ever go to a prossie? My guess is that it's incredibly unlikely.
The odd woman might, there have been female punters posting on punting forums that others I found credible vouched were genuine but its a tiny number. A more likely scenario is the female of a couple goes with her partner for a punt whether that's for him primarily, her or both.
WGs who advertise as bi use it as marketing in the main, they hope the thought of it will turn some punters on enough for them to book them, some do mention another WG they offer duos with though of course.