Not2, I think your gf has to solve any problem of this nature on her own, in her own time and as she sees fit. I know, if you were my boyfriend and started calling me bi when I wasn't sure or "out-of-the-blue" or hadn't even been thinking of it at all (and had other reasons for what you think you see) I would be offended. At the most, I would suggest, next time you see something that makes you think she might be bi-interested, that you mention your thoughts to her, see what she says. How you feel about her being/not being bi/gay/whatever is not the point; it's her sexuality.