Well it is obvious that she killed Ozai's father because he was going to kill Zuko. When Zuko's mother was caught by Ozai he kept it hush hush and became fire lord. Also Ozai must have orchestrated it to become king and thus fooling Zuko's mom. So, what happened to her? They say they'll reveil it in the last two comics, The Promise, part 2 and 3. I think she eloped with Appa, just saying.