Do you think i'm being rude?

I'm really shy by nature & work within a place of several , 6 of whom i work with closely and the rest is the "pleasant acknowledgment" but thats all. because i'm shy i feel insecure at times about being boring and being left out. the others are 7+ years older than me (i'm 23) yet sometimes act like theyre 16 and i dont really wish to join in. however theres one girl who is always sarcastic to me and has upset others as well as myself. in the end i sit at my desk, work and keep to myself because i dont like this girl much and when i do try, she is mean or simply pretends i'm not there. another worker acknowledges me but wont bother having much to do with me, am i giving off the impression i am there to work and thats all? i want to make friends with them but this one cow has to be centre of attention and being shy i end up alone and left out from "coffee breaks" etc as i choose to keep to myself and not put up with her rubbish. the others are wary of her but still want to be around her