Disclaimer, I won't do anything while she's taken, I'm just confused as she's one of my best friends.
To make a long story short, about half a year ago she broke up with her boyfriend. We were flirting not long after, all the while I was shortly dating other girls while she was after someone else too, then we had a bit of a conflict so we spoke less and when we made up I was already into someone else and she was talking to her ex again. Around then we had a convo about the tension between us in which she said that our friendship was too important to risk.
Suddenly (~3 months after the aforementioned events) her behavior was different. She was more physical and made "ironic" flirty remarks (could be explained by the alcohol). Then when we had a conversation about our love lifes (sober) she suddenly drops "I sometimes wonder how a relationship between us would look like/work" (though "not in a weird way", but saying that doesn't make it not weird lol). Not only this, but later I asked a hypothetical question of who she'd like to kiss from our (rather large) social circle if she were single, and again she eventually says "I've sometimes wondered how it would be like with you".
The day after I caught her staring almost absurdly long with an emotionless expression on her face. I had time to catch her, look away, look again and avert my eyes again and she was still staring. Tracing back when she became more physical/flirty also aligns with when I told her it was over with the girl I was into at the time.
I'm confused, she was the one to put up boundaries and chose someone else over me twice so it feels like I can't be interpreting this right, while my gut is telling me I am. At the same time she was apperantly under the impression that I was with other girls too back then so she might not have seen my flirting as serious.