If two men are messing with the same girl and they know each other either have or had been messing the same girl. (typically, this girl is a side hoe or not very important) The two men only have been using the girl for her head and her tail, hence the name, she is a coin ass bitch.
Hitler Youth: Bruh did she really just roll up to us like that?
JMoney: Yeah bro, we know she a coin ass bitch!