I think I use "girlfriend" specifically because of its ambiguity. I know what I mean by it, and I always answer honestly when people bother to clarify. But if people want to think of that as my friend who's a girl, or if they make the connection and whether or not they actually ask if I mean girlfriend-girlfriend? I'm not too concerned about what other people think or know. Part of me enjoys the game of keeping them guessing. Maybe I even like the scandalous possibility that people might think I'm having a (blatant) affair with a woman, if they get that far...
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker