What's the name of this movie? I can't remember!?

I watched this movie maybe 6 or 7 years ago on television. It involved a girl who had an eating disorder and was...well..obese. She was made fun of I think and felt left out. Then suddenly she became skinny and hot but had a huge appetite. At one point she is driving late at night and hits a deer. She is hungry and gets out to see if the deer is okay. When she sees it is dead, she can't control her hunger and her mouth opens WIDE AS HELL (more like long as hell) and she eats it. I think she wanted to get revenge on this one boy in her school that made fun of her a lot. She takes him to a private place and talks to him, then she turns around and eats him too, mouth gaping. The rest is kind of blurry, but it's just frustrating not knowing the name, I've wondered what it was for a long time. Help would GREATLY be appreciated :)