Princess Kimana

Princess Kimana was Iroh's wife in my story. She died of allergic reaction to accidentally ingest lychee nut dust that was thought to be tea spices. 

It was assumed to be an accident as the bottle was mislabeled. 

It will actually be confirmed to be murder as Akiko and Zuko guessed by Ozai during the events of Black Sun who purposely mislabeled that bottle knowing full well as did everyone in the Palace of his brother's wife allergy and wanted to knock her off in a way that no one would suspect as murder to limit Iroh's heirs and give himself more chances at the throne. 

As Ozai will say flat out he had no qualms with Azulon order to murder Zuko which would not only have murder Zuko but also kill Akiko as she would've died without Zuko since he'd already killed once already and as long as it got him anywhere close to the throne it didn't matter to him. 

Point blank confirming that he did murder his own sister-in-law just so his brother wouldn't have more than one heir and because he enjoys seeing people suffer so making his brother feel guilty for actually putting the 'poison ' in the tea is just more sadistic pleasure to a monster like Ozai.