Feeling out of control?

You are right in your last scentence. I would tell the girl's parents what happened. They need to get her help so that she can sort her problems out. Secondly it sounds like you've had a rough go of it lately and this is not something you need to burden yourself with. Tell her parents, urge her to get help, and offer her support but don't let her illness destroy you. Maybe also talk with a parent or a counselor or trusted person to get some insight and perspective.