I’m pretty sure that it goes the same way with just about everyone. If a guy does it, they are often seen as interested or “trying to get into her pants.” I can only imagine how people view people who are bisexual when they are completely open with others or flirty. The entire idea of flirting is to show interest in a person. Even if the girl is straight and just friends with a guy friend, of course from the outside it’s going to look like she’s into him. The key is that it is play flirting, and without context, it’s hard to tell from the outside.