Hi PeguinStalker, Welcome to healing well forum. I am glad that you felt safe enuf to post here and seek advice.
Unfortunately, most people don't stop to think of how their actions or words will effect someone else. This is true especially of girls/females who can be catty and vindictive.
My suggestion to you would be to seek out a counselor or physician at your school. I recommend this due to the fact that you have contiplated self harm and are isolating yourself.
Also is there a student advisor in your dorm? I would suggest talking to them about this too as it seems that there may need to be some kind of intervention taken with the other girls. Or they could give you some advice on what to do.
Please keep us updated on how it goes.