Hi Laura,
Is she scared of the dark, or scared of being alone? I ask because I was very scared of the dark when I was a kid--overactive imagination, I guess. (I couldn't tolerate a scary movie until I was well into my teens.) Although my mother didn't like it much, I just kept a light on. I fell asleep just fine with it. In fact, to this day, if there's nobody in the house, I keep a light on when I fall asleep.
But if she's scared of being alone, that strikes me as more complicated. I think the music might be a good idea. Have you tried the gradual withdrawal approach that I've seen and read about (Supernanny recommended it, among others)--where you're by the bed, then by the door, then right outside the room, etc.? Even though she's a bit older, this might work. I do think it's important to try to work on it actively rather than wait for her to outgrow it. I have a niece who is ten and still has this problem because it was never systematically addressed.
best,
daylily