Daughter being bullied

Hi – My daughter has had a rough couple of months. Her grandmother died over the summer, and now it looks like she may have Cushing’s disease (a tumor on pituitary gland that caused her to gain a ton of weight and stop growing). Last night we went to a party where her classmates were and they told her to go away– people she’s been friends with for years. She was pretty popular until recently, so she’s attributing this to her weight, which she can’t do anything about right now. Many, many things like this have happened over the past year. I, naturally, want to go set fire to those children but am trying to rein it in. But I don’t know what to do for her — I know everyone has to suffer etc but she’s had more than her fair share and I want to give her a way to look at this that will make it less painful.