I get what you mean about a metaphor turned into a person, and I think no, it would have to be an actual character, because the idea is that you're using the song as the backstory for the character. So, Mary Jane the girl from Indiana would work. Mary Jane as a drug reference then turned into a character, no.

And 2/3/59 (http://en.wikipedia.org/wiki/The_Day_the_Music_Died)