ganga

-A female who part-takes in gangbangs
-Someone disgusting enough to lower themselves to a gangbang
-A whorish/slutty looking girl

The girl doesn't actually need to be a ganga to be called one.
Disgusting girls can also be called ganga's as well as girl's who have the appearance of being easy, cheap and dirty.

"Omg that chick is such a dirty ganga"

"That chick looks easy..." -"Yea, I heard she's a ganga"