You know that "demons" are just a figure of speech, right? There aren't actually demons, that can win or lose. There's only the individual. I suppose she was talented, as she had 2 records, one of them a hit. She was also quite popular. But she died because she was addicted to drugs. There were no outside forces acting on her.
Not that I was a huge fan or that I'm following this religiously, but I just wanted to point out that it appears as though alcohol might have been her ultimate problem. Same problem and same results, of course.