Sigh, usually cancer onset on such an early age isn't caused by environmental or lifestyle choices. It's all in the genes. Changing her diet and forcing her to stay home isn't going to help one bit. Should just let her carry on her life as usual with her friends and schoolmates and follow the oncologist instructions. There's always some auntie or uncle that come and say "this xxx is good, must take a lot" or "must avoid xxxx later cancer come back" or some crap like that.

I strongly believe forcing her to change her lifestyle and forcing her to adapt to "old people sayings" are what drove her towards suicide. My mom was diagnosed with cancer a few months back and I've tried putting myself in her shoes, with all the nonsense and "advice" from the more elderly. If I'm forced to follow their instructions, I would probably do the same as her.

Anyway, I'm not a psychiatrist, that's just what I felt when I read the story. Best is still to bring her to a good psychiatrist and try to understand why she did it. Then please, listen to the professional's advice and don't try to become experts.