So

The girl I'm dating just told me she's "genderfluid".

What does that even mean? Could I just be making out with her and she goes "oh btw I'm a guy right now"?

Does that mean I'd have to be Bi to continue dating her? lol.

Questions questions questions

"Gender Fluid is a gender identity best described as a dynamic mix of boy and girl. A person who is Gender Fluid may always feel like a mix of the two traditional genders, but may feel more boy some days, and more girl other days.
Being Gender Fluid has nothing to do with which set of genitalia one has, nor their sexual orientation."

You know how a trans* person feels like the opposite sex? A gender fluid person goes between the sexes in which they feel like.