I'm also a bi female. I've been with my GF for about three years. I'm out to everyone about having a female partner. And I'm out to my family and friends, but not most of my colleagues at work/school about being bi. I bring my partner to school/work social events so people know about her and they probably make the jump from "she has to female partner" to "she's a lesbian." I think my family can be a little confused about it sometimes too, because they've made comments about me not being interested in men and then I correct them and they look a little like

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I've been going to a therapist to talk about issues related to work/school and sometimes I talk about relationship issues. The therapist seems to be totally good with gay and lesbian issues, but she seems to have had some trouble with knowing how to deal with a bisexual client. I told her that GF and I are thinking about having some type of commitment ceremony but that we also are hesitant about it for all sorts of reasons (none of which have to do with not wanting to make a commitment to each other--mostly issues about money, family, what this event would be like, etc.). Then later when I mentioned being bisexual she right away said, "Oh, so does your being bisexual have anything to do with your being hesitant to have a commitment ceremony?"

Uh no, why would it?
GF and I are monogamous, though we do have a clause that says, essentially, that we are both open to reevaluating that status in the future, though there's no guarantee that after reevaluating we'll decide any differently. So for all practical purposes we are monogamous. I talked about this with the therapist and right away she connected it up to me being bisexual and said something about how being attracted to both sexes I might have "different needs" then other people and that might include non-monogamy. She even implied something about GF possibly being bi--as if she just assumed "Oh, the partner is open to considering the possibility of non-monogamy...she must be bi too." (Actually GF identifies as a lesbian, and of the two of us, she's the only one who's had a non-monogamous relationship in the past.) I was just like "Huh?"
She seemed to really have this thought that deep down I really can't just be with one or the other sex. Eventually I just came right out and said, "Uh no. My being bi has nothing to do with this. I happen to be attracted to both sexes. I fell in love with someone who happens to be a woman. I'm also attracted to people of all hair colors. I fell in love with someone who happens to be a brunette. My attraction to both sexes is no more connected to our possible non-monogamy clause than my being attracted to people of all hair-colors is."
She must think I have a much, much, much more exciting sex life than I do
Rosie and Tinker, do you have much of a gay/bi community that you are part of in real life? If not, is that hard for you? I came out as bi in college (I was already part of the gay community as an ally at that time) and then a few years later got involved with GF, so I haven't actually spent a lot of time being bi and single, and I've never been in a relationship with a man. So I've always been involved in the gay/lesbian community since before I came out, and when I came to grad school I just accidentally ended up knowing a lot of bi people. My roommate for awhile was actually a bi woman who was doing PhD research about bisexuality. That was a really great and welcome change from college where some friends "didn't believe in bisexuality."