I need Women's Answers -- Men can Answer too. This girl is flirting with my boyfriend and I don't know why :( ?!

I trust my boyfriend not to cheat, but he told me something that really upset me today. We go to different colleges and he teaches(ta)as a part time job. Last week he introduced me to his classes and told them I was his girlfriend. I just sat there and watched his lectures and wasn't loud or anything. My boyfriend told me tonight over msn that after class this one girl came up to him. She is doing poorly in his class, sits in the very back corner, is quiet, but doesn't pay attention. He said she is pretty and is my height, thin, tan, blonde, green eyes, and wears hardly any clothing. Today she came up to him after class and was trying to push her boobs together with her arms and show her cleavage and asked him one subject question and then asked him numerous questions about ME. She asked how long we had been dating, my major, where I lived, etc. She never spoke to him before he introduced me to class.
I feel jealous because (although I didn't see her), she sounds pretty good looking...I am her height, thin as well, with blue/green eyes, auburn hair, and I'm pale but have acne :(
Why do you think she suddenly began acting this way.?
If she liked my boyfriend then wouldn't she have at least tried getting decent grades or have asked for help before and why did she ask about me when I hardly made an appearance.?
Thanks for the answers>< Health Question & Answer

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