This is what Mike and Bryan said about Azula:
Exclusive interview with Bryke found Sozin's Comet Book P.g 63.
Is Azula really as evil as she seems ? Or is there more to her?
Mike: As all the Avatar characters , even Azula has a softer side , though she buried it very deep. As the Beach and Sozin's Comet showed ,she has a lot of unresolved issues with her mother . She really feels that her mother did not love her as much as Zuko , and this drives her crazy , literally.
Bryan: There are truly evil people in the world , but in the case of Azula , her repressed emotions and jealousies corroded her spirit , and made her become that way. It is possible that she could turned out better in a healthier environment, but growing in a royal family of a nation seeking world domination exacerbate her problems . But Zuko and Katara spared her life and who knows she might have a chance to heal."
Ozai was the cause of suffering of Ursa,Zuko,Azula, and Iroh.