*if you havent finished it dont read, possible spoilers* I think that elevens character was basically a metaphor for a girl who was abused and killed herself. Think about it. The demogorgon got released and all that because of her mind and who pushed her to set it off? Her father. It was in her mind, it was her inner demon who she had to fight, and when she killed her demon, she killed herself. And the boys were her friends who were helping her to fight her demons (depression) , but in the end only she could kill it. And Joyce is like an adopted parent (thus why 11 stays with Mike in his basement) when Joyce said "your very brave, you know that?" In the last episode i think thats a metaphor for telling her how brave she is for fighting her obvious depression (She was getting weaker and they didnt know how to save her. Her depression was worsening) She was running from her past, and when it caught up to her and she was face to face to her demon, she died while fighting. Just a theory tho, but interesting to think about.