The female version of the friendzone
. This phrase is used to indicate a female who is viewed as a platonic, non-sexual entity to a male or group of male friends. The moment a female is referred to as "one of the guys", she becomes aware that if she has any romantic feelings towards any of the males in the group (or, specifically, the male who referred to her in that way)--it is a moot point. Her male friends will come to her to talk about their bad relationships or advice on what gifts to get their girlfriends. If she does get a boyfriend outside of the group, they may find it very difficult to accept her any longer--as there is now competition for her time--and it may bring about the abrupt realization that she is, in fact, a "girl".
Anna: Oh, hey guys. You all got dates for the party?
Anna: Oh, well, we could go together, Arthur.
Arthur: Haha, no! You're like 'one of the guys', Anna. It would be like going with Alfred.
Alfred: You wish.
Anna:.....ah. I see.
Elizabetha: Hey, Anna--did you ask Arthur about the party?
Anna: Yeah. He told me I was "one of the guys".
Elizabetha:....oh. Sorry, Anna.
Anna: I don't get it--am I ugly?
Elizabetha: No, no--they just look at you like a sister. Completely platonic.
Anna: I thought guys didn't do that.
Elizabetha: Well, the media says they don't---but they're actually just as human as us.