I hear what you're saying. For you, it had nothing at all to do with homophobia. She just wasn't invited for whatever reason - she just wasn't a part of the group that was invited.
Trying to understand her side, i would say that when someone has experienced a good amount of discrimination in their life, they come to expect it. Coming from that perspective, it follows that when she wasn't allowed into your party, and didn't understand it, she went to what she is used to. Homophobia.
Maybe she has even had experiences with bi people who hide their bi side and blow off their gay friends when they are around their straight friends. I'm not saying that you did do that - I'm just trying to understand what her life experience has been.
If she is important enough to you, maybe try to give her an explanation that she understands so she can see that it wasn't homophobia.