This other girl in my bio class started to like me: it was really obvious, she'd always talk to me nervously, touch me on the arm, ask me to "study" with her, text me and ask me if I got the texts, etc. So when she began sitting at the same table as the first girl and me, the first girl pretty evidently got jealous.
I say this because the first girl noticed the attention I was getting from the second girl, then started calling her my "Girlfriend" in every sentence, got visibly upset when I decided to do a lab with her instead, and then started to complain about her stealing our lab secrets. Then one time when I studied with the first girl, she kept asking me questions about the second girl.
It really started to annoy me. This girl already has a boyfriend, so why is she trying to sabotage this potential relationship I have with this other girl? None of the stuff she says is tongue-in-cheek or joking, it's always mean-spirited and she always tries to get the other girl in trouble or make me feel bad about reciprocating that attention.
It's gotten to the point where the girl who has a crush on me is afraid of sitting at the same table now because of the rudeness of the first girl
Most Helpful Opinions
Set the boundaries between the first girl and yourself, firmly. It sounds like she is used to getting her way all the time, and doesn't know how to respect others.
Let her know the next time she pulls something like that, that she has gone to far. Stand up for the second girl, not only will the second girl appreciate this immensely, she will find you even more attractive, and will help build a strong relationship once she sees that you can protect her.
She will also see that you have a strong sense of morals for doing this. The first girl hasn't seen any sort of deterrence from you, so she may see that as a go ahead to do it again. You have to stop this. It isn't right, and you obviously like the second girl.
The second girl seems like girlfriend material, where as the first girl sounds like a brat.
Go for the second girl, and put the first girl in her place.