Ursa since she was a child, had done her best to live her life without regrets. It had been a lesson passed down to her by her grandmother, who said that it was regret that ultimately killed her grandfather. She never pressed her grandmother about what she precisely meant, but taken the lesson to heart because of the desperate and honest look in her grandmothers eyes when she said it.
There had been many bad decisions Ursa made in her life, she didn't deny that. But she had always been able to convince herself that ultimately she was happy where she was, so whatever she had done was either not so bad, or had helped her get where she was today.
She had almost regretted her marriage to Ozai--after there wedding, there were times when he would say something terrible, usually in reference to his brother or nephew, or seem apathetic when something awful happened, and though he never was cruel or mean to her, it was his apathy or few comments that scared her. But she did love him, and he gave her two beautiful children whom she loved so much, she'd just have to look at them and any possible regret would quickly fade away in love for them.
Until Azula got older.
She didn't know what happened with Azula. Maybe she doted on Zuko too much, or didn't try hard enough to bond with the girl when she was a baby, or let her go off on her own too much, or shouldn't have let her father give her those extra lessons because she was such a prodigy.
But it was none of these things she really regretted. She couldn't have known at the time. There was no one who warned her that her daughter could turn out so unexpectedly violent or cruel.
Her regret wasn't even the terrible and treasonous thing she did to make her husband Firelord, and eventually Phoenix King.
No, the one real regret was the one comment she had made to her handmaiden--one that she knew even a she said it was a terrible thing to say. It was after she had caught Azula practicing firebending on her friends--the two girls were quite agile and amazing with their dodging, but while that was dangerous and terrible to put her friends in danger as it was, one of the noblewomen was also out in that section of the garden with her newborn baby. As Azula aimed her fireblasts at her friends, she was just missing the woman, and the woman couldn't leave because she was nowhere near the exit and couldn't get to it.
"Azula! Stop it!!" Ursa ran out and grabbed her daughter's arm. The noblewoman quickly ran out of the garden and back into the palace. When she saw the woman leave, Ursa focused back on her daughter. "Do you realize what you were doing?"
"Practicing firebending!" Azula snapped, her tone obvious like Ursa would be an idiot to suggest anything else.
"You could've burned that woman and her baby--or even your friends!" Ursa reprimanded her.
"So?" Azula replied. But unlike Ursa expected, her voice wasn't sarcastic or baiting or purposely cruel. She was genuinely confused at why burning someone would be such a problem. And it stunned Ursa so much, she couldn't even answer her daughter. And when she only got silence, Azula apparantly got bored and pulled her arm away from her mother. "Come on girls, let's go somewhere else!"
And as the girls ran off, Ursa just stared after her. And assuming only her handmaidens were around her, she simply commented despite feeling horrible about her words "How did that girl become such a monster?"
But either her daughter had better hearing than she realized, there was someone else in the garden, or one of her handmaidens decided to share that moment with someone else. But Azula somehow found out Ursa said that. She suspected it later on, when her daughter's actions became more blatantly cruel or obviously devious, but it wasn't until she was dragged back to the Fire Nation capital, after her daughter was crowned new Firelord, that Ursa discovered for sure that Azula definitely knew about her words all those years ago.
"Welcome back mother. What do you think? I've become the youngest Firelord in history! Know how I did it? Of course not, you've been away, but would you like to hear?" Azula taunted her.
"Certainly Azula," Ursa replied calmly, watching her daughter carefully as she circled her, and made the flames around the throne room grow and fall erratically.
"Well, your favorite son Zuko came and tried to stop me from being crowned Firelord, even though dad had already picked me. He challenged me to an Agni Kai! And he brought some Water Tribe peasant to try and stop me too. How pathetic is that?" Azula laughed. "I admit, they put up a better fight than I expected, but in the end I won."
Ursa's heart stopped for a moment at the thought of what that could mean. "How did you win Azula?"
Azula stopped circling her and stood in front. "You mean what happened to your precious Zuzu? Don't worry, he's not dead, and I'm sure he would be more than happy to see his mommy after having to watch that pathetic girl get burned alive. Although I think death by blue flames are a pretty appropriate method of death for a waterbender don't you? ...DON'T YOU?" Azula shouted and slapped her mother when Ursa didn't answer.
"It is certainly ironic and works in an aesthetic sense Azula," Ursa answered after scrambling her thoughts.
"No, call me what you really think of me!" Azula yelled and hit her mother again. "Tell me what you think!"
"You are my daughter, Azula," Ursa tried.
"No!" Azula hit her again, forcing her mother to fall over. "Of what I've done, say it!"
"I do think you're somewhat out of control," Ursa admitted still calm as she got up. "But that's to be expected since you are so young with so much power..."
"NO!!" Azula shouted and grabbed her mother by the front of her robes, the fire in the room blue and high with Azula's anger. "You think I'm a monster don't you? Say it!!"
"...I don't think that Azula," Ursa told her, voice steady and staring at her daughter's eyes.
"LIAR!" Azula shouted and shook the older woman. "I know you think that of me! Don't pretend to be proud! You're disgusted! You think I'm horrible! You think I'm a monster!"
"You're not a monster, Azula," Ursa argued softly, voice still steady and honest. "A monster doesn't need validation. A monster would've just burned their defenseless mother alive the moment she was brought before her. You're just confused and scared, Azula. But you are not a monster."
"LIAR!!" Azula threw her mother across the room and grabbed her head, her eyes scrunched shut and shaking. She then took a deep breath and brought her arms down as the flames around the room settled a bit, and opened her eyes slowly. She then spoke to her gaurds. "Throw her in the same cell as Zuko. Maybe seeing her favorite child in his current state will change her mind. Get her to be honest with her own daughter and current Firelord."
But Ursa knew her mind would not change. Even when she saw her son shaking with terrible burns and curled up in a painful ball. Azula was not a monster. She had been wrong all those years ago. Even with all of the horrible things she's done since, Ursa knew her daughter was not that awful. She wouldn't be so demanding to hear her mother say it, she wouldn't let her brother live, she wouldn't reunite Ursa and Zuko. Azula needed help, absolutely, but she was not an evil creature beyond redemption.
Because no matter what Azula did, no action could be more monstrous than calling your own child a monster, could it?