^^^ I'll second that
...was it because you (Tangled Web) were trying to be so emo or metrosexual that you thought she would be a little turned on?. If your being serious...then heres my take...even a someone who is with the same sex, who reveals to thier partner that they are bi...may have been met with the exact same reaction. A gay person, who struggles with their identity to be accepted by friends, family...the world etc,...hears this news of their partner, it is then that they no longer feel like you share the same inner turmoil and acceptance issues...call it unfair...but there are bi's who are more one way then the other...but its looked at as someone who is also afraid to be themselves, and be real, even if what you thought your were doing was being honest...it seriously is unfair for anyone to be met with those accusations...but this does happen...the bisexual community is looked at as being more about sexual expiramentation rather then sexual orientation...and the gay community is a way of life, its about being aware of who you are, what it means to be gay, and oppression. Just because you have your Will and Grace shows on TV, or Brokebacks going to the Oscars...doesn't mean the real issues are resolved. Our Countries leader is openly opposed to gay marriage and civil unions...this translates 50 years ago to saying you are pro segregation.
But lets just forget I said all that and assume that perhaps...she may have thought you were implying that the next thing you were going to want was a threesome...with another dude. Or that you were going to convince her, that she should try being bi because you are, and eventually talk her into having a threesome with another girl. You were trying to open up a whole other world of expiramentation that she probably just wasn't ready for, or ready to do...um...to you. Nah'mean.
respect her decision...and learn from your mistake. Trust.