This came up in a polite conversation the other day, and we couldn’t agree on an answer.
Assume A, a hetero guy, is dating B, a bi girl, seriously for, say, several months. No explicit “ground rules” are set at the beginning of the relationship. B goes out with her friends, including C, a bi girl. Drinks are had, and a makeout session ensues which develops into full-on lesbian sex.
Has B cheated on A?
My position: Absolutely. Relationships are emotional in nature and not gender-related; to assert that relationships are at their essence gender-related would be to deny that a gay or lesbian couple can have a relationship. As such, unless A gives B his permission to date other girls, B doesn’t simply retain the right to sleep with girls any more than A has the right to cheat on her. (Of course, this isn’t to say that they have any control over each other, any more than the normal courtesy/agreements involved in a monogamous relationship.)