How to help a friend out of a deep depression? Desperate for help.

Sorry if this is long but I'm just so desperate for help here. I have a friend group of 6. We've been friends for a while and two people (Christina and Stephen) always had little crushes on each other. They started dating and that went on for about two years. Right before we left for college, Stephen suddenly broke up with Christina. When I say suddenly, I mean it. We were all happy and getting along perfectly. They had plans for the future and were really excited. Two days after we all went on a little senior week trip, he just ended it with her. He said he saw no future and didn't care about her anymore. Everyone in our friend group was so surprised. Stephen's best friend tried talking to him but he said nothing happened, he just wants the "college experience." Fast forward a bit and they both are extremely depressed. Christina did not attend any of her classes. Not one. She was kicked out. She barely eats. She's lost a lot of weight and pukes up everything she eats. She doesn't do it purposefully. She won't speak to anyone. Stephen attended and did well in school but also doesn't talk to anyone. He will go places with us and won't say a thing. You ask him a question and he gives a one word answer. He didn't have his "college experience" so it makes no sense. I have no idea what happened but I'm just so worried and confused. My best friend is going to die if she continues this. She doesn't get out of bed. She is a zombie. We need help and I don't know what to do. Her parents tried getting her into therapy and she won't go. If they make her, she doesn't say anything.