I have no idea about the nicknames, but I am ABSOLUTELY CERTAIN that she has the best sex with Six. Of that, there is NO DOUBT IN THE UNIVERSE.

Oh, and I think she and Benny have raided the TARDIS wardrobe, gotten piss drunk and shagged like bunnies on more than one occasion. While on a mission to steal priceless artifacts and avoid the cops. And Seven was busy being all secretive and distracted. This is my personal canon.