So I had been hooking up with this girl at school for a few weeks (never really texted her or anything, just ran into each other at parties and we ended up together) and saw her last weekend at a party again. So I just did my thing at first, tried to enjoy the party and approached her later. But before I did I noticed she was all over some other guy at the party, yet I could feel her staring at me the whole time. So I wasn't really affected by her hugging, touching and flirting with some other dude so I just waited till they separated and walked right up to her like everything was cool, but after about 1 mintue of talking to her she literally just walked away from me and went back to the other dude. (No I didn't say anything weird, I talked to her like I had the previous times and she just left).

Now obviously I'm not interested in her anymore but was wondering where I messed up, for next time? Was I too predictable, did I not show enough interest (over text or anything), or did she just get bored and there's no real reason why?