Nice "friend"

[Lindsey]

A lot of you might remember awhile ago I was having problems with my "friend" who was staying at my house every night because she's "secretly dating" my roommate. Well, it's still going on, she's been here every night since. I tell them to be quiet almost every night, and they usually listen. Anyways....
Last night I was talking to one of my best friends from back home. She asked me if I heard about this guy from our hometown, and I said no. I thought she was going to tell me he's getting married, or something about hockey... but no, she tells me he was in an accident. Now, I don't know him WELL, and we weren't friends, he's probably about 6 years older than me, but when you grow up in a town of 500 people you know EVERYONE. He had an after-school job working with my mom, his parents were the school janitors, his sister did my makeup for grad. So, last week he clipped a semi in his car. The car rolled and he was seriously injured. His leg was broken in 5 places and he had internal bleeding. He lost his leg, but he could be saved. BUT, he's a Jehovah's Witness and couldn't get a blood transfusion, so he died. I was in COMPLETE shock.
Not long after I found out, my "friend" messaged me on msn, saying she has the book I need for a school project. I told her don't worry about it right now, I was taking the night off homework. I told her what happened and how upset I was. I said I didn't feel like doing anything, and I was just going straight to bed, and I did.
An hour later, she walked into the house, woke up the dog, woke up me. She went straight downstairs and her and my roommate started playing music to cover up their sounds. They were laughing and giggling all night.
Today I went to school grumpy. I sat there and didn't say a word to anyone. She walked into the room and sat behind me and said "Hey Lindsey, I can see your bra strap!" I didn't even move. Class was cancelled so I went to put my books away and go home. Another girl came up and asked if I was feeling okay today, and I said yeah i'll be fine, and then my "friend" was like "yeah are you doing okay? are you still in shock?" pretending to be all nice and sympathetic in front of everyone else.
I don't know what to do about her anymore. I'm done here in 8 weeks and I'm counting down the days, but I don't know if I can go that long without just exploding.