She really was. I know Zuko put her high on a pedestal, because his father was completely awful, and he needed to have one parent he could idolize, but she really was not much better than Ozai. Yes, she did stop Ozai from killing Zuko. However, she killed Azulon to do so and abandoned her children, even when she knew Ozai had it out for Zuko. As discovered in The Search, she chose to forget about them! I mean, what mother choses to forget about their children?! I don't care if she thought living with the memory of them would be too difficult; that's just incredibly selfish. Two young children depended on her existence, and she chose the easy way out for her to forget them. That's nice for you, but what about your children? I mean, clearly, both of them turned out to be basket-cases, and if she would have remembered her children, maybe she could have helped Zuko when he was banished, along with Iroh? Maybe she could have helped Azula before she went crazy? Even when she was there, she didn't bring them up in a nurturing environment.
Azula went crazy, because she thought that fear was more powerful than love. She thought her mother hated her, and feared her/saw her as a monster, so she rolled with it her entire life, using fear to control people and become the monster her mother thought her to be instead of letting people in and actually forming bonds out of love. However, it backfired when she discovered that she had no real power over her friends and family, because they didn't fear her, nor really love her at that point because who could love someone like that? But Azula was completely right. Watching Zuko Alone, Ursa clearly favored Zuko and feared what Azula would become one day. She tried to correct the behavior in small, futile attempts and never showed Azula that she actually loved her; she would say remarks like, "what is wrong with that child?" We saw Ursa have loving conversations with Zuko but never Azula. Azula had to create that loving-mother picture out of her own mind, basing it off of what a mother should be like to her child. Her assumptions, which may have been right, led to her demise. Her whole life, on the surface, she felt her mother hated her and that helped drive her abilities (remember anger fuels firebending...at least that's what Zuko was taught before he visited the dragons). She found out that love was more powerful than fear (Mai protecting Zuko, Ty Lee protecting Mai), something her mother could have shown her at the beginning and eventually did through Azula's own doing. She knew that her mother loved Zuko, so hopeful thinking would tell her that her mother must love her too deep down. Someone, the someone (her mother) who sent her down this path of chosing fear over love, actually loving her instead of fearing her? And this love was better than fear? Had she misunderstood everything in her life? Was Zuko better off now that he had real friends and people who loved him? Was she all alone? Her mother, the only one who might have loved her, was gone. That's what drove her crazy.
Zuko spent most of his life thinking about his mother, trying to track her down or assuming she was dead. Deep down, he thought she was dead, as seen by his tears during the eclipse when his father tells him that she was only banished and is probably alive. Is that fair to bring that burden on you children while your living in bliss because you chose to forget them? In my opinion, she was a bad mother.