The way she said, "Everything I've done, I've done for you" to Zuko (i.e. Azulon was going to make Ozai "lose" Zuko the way Iroh lost Lu-Ten, so Ursa killed Azulon before he killed Zuko). This is kind of backed up with the turtle-ducks scene where she's like "If you mess with a mom's babies she'll f your day up". And then in the Day of Black Sun (this is a SPOILER if you have not seen it!) Ozai says to Zuko "Your mother did treasonous things that night".
Oh my God... That is just perfect. I don't think I've ever seen horny!Azulon before, but I can so see it now... Wow, there are Azulon fans out there? Not that it's a bad thing, they've got to be awesome to talk to. lol
This really reminds me of the fifth part of this meme, BTW: [link]