A Tokio Hotel fan(girl) whose favorite member of the band is Bill Kaulitz, the singer and frontman. Probably about 80% of all Tokio Hotel fans are Bill girls, with some Tom girls and those few diehard Georg or Gustav girls mixed in.
(sitting in a concert line)
Fan 1: Look at that chick. Her hair's in a huge mane and check out that leather jacket.
Fan 2: She's obviously a Bill girl.
(fans meeting for the first time)
Everyone: So who's your favorite?
Everyone: Oh, I'm a Bill girl. XD