Why is she talking to me?

Ok so theres this girl in my class who joined our coll last sem(3rd) and now were in the fourth sem and before it used to be just a hi bye relationship but come 4th sem and she is talking to me like crazy for God knows what reason. Im a really secluded kinda person and an introvert so I got the feeling that shes talking to me to get me talking because on one occassion she told her friend that hes(me) started talking finally so let him talk(wen that friend interrupted me). Now shes become close friends with a girl who I know since 1st sem in our class. I overheard this(new) girl telling this girl who I know from before that she has a bf. He even came to meet her at coll once. Then why is she pursuing me??. I mean she always calls me wherever she goes in coll and expects me to hang out with her in coll(is it because I always walk alone in coll??) . She even tried to take my number but unfortunately that did not happen. She says hi to me everyday and shares her food with me always.we are both 19 if that helps. Im so confused because at one time these two are talkin about her boyfriend and at another time they(the girl who I know since sem 1 and the rest of d group excluding this new girl) tease me with this new girl and start pairing up us both. So is she actually goin out with someone and if she is then why give me a lead??. Secondly why only me ,why not anyone else(there are so many single guys in class).