Hi makes sense to me. People are often just courious what other people are doing and wanting to try it doesnot indicate they are bi.
If she has been your girlfriend for 7 years and presumably the two of you have a good sex life, unless you think she is cheating, don't worry about what videos her curiosity leads her to watch. Often women find girl-girl porn stimulating because they know what it can feel like to have those things happen to them. (Men in the same way relate to men in heterosexual porn -- they are turned on by the looks of the women but can understand what the man must be feeling too, which makes it a one-two punch.) I don't know why your heart sank at seeing lesbian porn on her phone unless you have other insecurities in the relationship and this just brought them to mind. She's with you, right? Not some girl.
I think you can rest assured she's bisexual. Or maybe a lesbian, but she's been reluctant to live that lifestyle.
Why are you "dating" a woman for 7 years without a commitment, by the way?
Are you living common law.? ( i know that not all secular couples go in for making the commitment formally; but again, that doesn't mean that a partner might not want to be genuinely and seriously asked , especially after 7 years.)As for the girl on girl porn. I think many women touch on this subject however briefly in their lives. This might be that, an almost casual reference for her, or it could be something more. Even acting on it would not mean anything more than bi curious imo. and i don't think that most people do act on curiosity, so at this point, i wouldn't let it wig you out. Try to communicate and ask what she's thinking.
Well, I'm a lesbian and I sometimes watch gay porn with men, and rarely also straight porn, and I'm neither straight nor bisexual. It's not about being attracted to the people involved, but that the actions can still be stimulating.
But even if she is bisexual, so what? Bisexual people can be in committed, monogamous relationships like anyone else. She's been with you for seven years. Is it just that you're insecure about her finding women attractive, or do you have any other reason to be hung up about it?