Why has she gone cold on me?

Anonymous
I've liked this girl for 2 months, and she's been quite flirty at times with me. There have been times where she has been distant to me though.

However today it was almost as if she barely acknowledged that I was there. She would say the odd thing but she seemed quite when I tried talking to her. Admittedly I didn't say a lot to her but that was some kind of reflex I guess. She'd talk to a few people around me and be reasonably chatty but with me she seemed a lot quieter, barely making eye contact or anything.

She's been speaking to this guy for about 2 weeks now, and there have been signs that they're interested in each other, but I'm not sure. But since then, she's been quite distant with me. Now, I've done nothing major to show that I'm interested, but nor have I done anything to offend her. Before they got talking, in fact the last time I saw her, she was being very flirtatious with me.

Why has she gone cold on me?
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