I liked her true ending.
So what if she's working with the bad guys, she may become a more important character through this. And we know she isn't actually evil, she's only doing this to save her one true love, isn't that an admirable goal?
An admirable goal lost its admirality if it was done through devious way of evil.
In regards, she lost her true characteristics of being a kindhearted woman who cared for everyone. Now she became more like 'This world revolve around Arakune only'. That was why I think the bad end seemed better, because regardless of how bad she ends up, she stays true to her kind self rather than degrading herself to the unhealthy obsession and ends up betraying just about everyone that trusted her. I could go on for lists, but I'd limit myself to that for now.
Don't wanna sound like a hypocrite. Sig will be as gloomy as me.