This waste of (a vast amount of) skin realized in the 6th grade that she will die alone after welfare and multiple heart attacks. After this harsh realization, she desperately attempted to form friendships with attractive girls for the sole reason of leeching of their hotness. Ten years later, she's managed to hold together her parasitic friendship with these girls. When you and your buddies approach these girls, the grenade's callousness from years of fat jokes kicks into overdrive, and she does everything in her power to keep her "friends" from hooking up. The grenade will most likely have to be jumped on (read: get taken back to her place and spend many long hours trying not to vomit from disgust) by you or one of your buddies (probably whoever gets the short straw).
"She was the grenade" should be an acceptable defense in murder cases.