User blog comment:Zathronas/Speculative author: Who is Summer Rose?/@comment-24198837-20140809070112/@comment-24218038-20140809075231

So the sacrifice part was towards Ruby? Not spending enough time or such?

How could you leave me when you swore that you would stay?

So that would mean what? She promised to stay but her duties as huntress left her more away than at home?

''But, baby, please don’t do what I did; I don’t want you to waste your life in vain.''

If you theory is correct, that would mean she thinks her time spent trying to make a better world for Ruby was spent in vain.

But then she says

You’re not the only one who needed me; I thought you understood.

wonky a bit but plausible

I still think her sacrificing herself fits better in the context of the song but we'll have to see.