A girl I like who has a boyfriend showing me mixed signals?

So I met this cute girl at a college job and I've been super into her since. Known her now for about 2 months. At first she would switch from between being really engaging and flirty to very distant, sometimes within a single conversation. When I still didn't have her number and I wouldn't see her for a while, I swallowed my pride and looked her up on fb and added her (had 0 mutual friends) and fb messaged her asking for her number, and she gave it to me. Clearly she could see I was into her, right?

When I text her she would reply extremely late, like I'm talking sometimes two whole days, but she always ended up getting back to me right before I showed up to work, as though she didn't want me to be mad at her? I invite her to a party at my apartment, and what do you know she shows up with a guy who she introduces to me as her boyfriend. Just out of the blue.

After that night I mentally give up on her, stopped texting her. But then a week later on a Saturday night she randomly texts me asking if I knew of any parties. Now this is a really attractive girl with many friends so why would she ask me of all people?

Up until now these observations are not very definitive, I know. But then one day at work, I'm talking to her, just us two, we're facing each other and then all of a sudden she pulls her swivel chair close to me, grabs two other chairs and she props her legs up on them, spreading her legs in splits fashion. Wearing super short shorts that barely covered her crotch. Very deliberate and kept eye contact the entire time.

Now she acts very hyper and energetic around me i in the company of others but becomes calm, slightly nervous when talking to me alone. I'm wondering, is she considering jumping ship but doesn't have the guts to break up with her current bf? I also see myself very good looking, fyi. I meet a lot of girls that I like but I always put them off because I am in love with this one. Any analysis or advice would be greatly appreciated. Thank you!
A girl I like who has a boyfriend showing me mixed signals?
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