Are female gang members also hoes?

No, those are not hos. It's tricky to both kill people and gang members, because after a certain "gang wanted" (or police wanted) rating normal civillians stop spawning. Also, having high police notoriety keeps gang members from spawning, and vice versa.

Find a group of Morningstar gang members, and anger them, and then go around killing hos while keeping your gang rating above one star. When you start to get to around 3 police notoriety, back off on the civilians and max out Morningstar.

As far as actually enacting this plan, I found for this one the easiest thing to do was roll up in a tank. Just destroy the heck out of every civillian and gang member you come across, and he'll show up pretty quickly. I couldn't tell you if I managed to kill many or few hos, I just wiped out as many civilians as I could and hoped that somewhere among the bodies were some.

Many of the assassination missions have opaque or downright odd requirements, and I don't find that they are 100% accurate, either.