Search Results: girls acting like their friend

So this guy hangs always with this one girl (with her in group or they are alone) for past 3 months of college. She meet his good friend from my college (she hugs and is really happy when she seed him) and have one on fb from his high school. Some people from their group of friend think that there's maybe sth between them.

I meet that guy in one group before college and i saw him there 2-3 times in period of 3 months. He was really talkative, bit show of (he liked attention i guess). I didn't think that he even noticed me till next time. He would stare and look at me and we locked eyes few times, we flirted.
After 3 months started college, we are on different ones but in same building. He always notice me, looks and stares at me, become quiet when im close even with his friends, and when i move he become talkative.
If he couldn't see me he would move to place he could. We would act sometimes really silly, like he doesn't even notice it. He looks at me and acts stiff even around that girl when im around. With her his normal. When he saw me with his good friend he was walking with that girl through my college and had perfect timing and he couldn't do it unless he knew that we would go there and with that timing.
He's been acting like this for 4-5 months now. This when he started to hang put with her more didn't change he acts around me.

What's going on? Why is he acting like that? Are they just friend or what?