I think so.

I think it's a bit of vengeance and spite.

I think it's fueled by a malicious happiness as weird as that sounds. I feel like she wouldn't be able to show all the control and precision she normally does if she was fueled by those more depressing emotions. She be a lot more like Zuko, always ready to blow up. That's not to say she doesn't have these emotions. I think she just bottle's them up though and doesn't use them as her focal point. It explains why when she has her break down, and is finally feeling all that anger and sorrow that her fire bending is so much less powerful.

Interesting question. Though I think I'm with Aang_Lite she has kind of this sadistic thing going on. But then I also think that it's powered by her need for perfection as well and constant practicing of her bending. Basically what Aang_Lite said, despite what both Azula and Zuko would like to think they are more alike than they think...if she used anger or sorrow all the time it'd turn out how it did in the comet.

I think it's both. To me you just can see all of the emotions going through her

Especially in the end...really emotional finale.