Herd of fire.
Azula and Zuko constantly fought over who would be the Alpha of the pack.
Mai and Ty Lee accepted Azula as their Alpha, because Zuko was rarely around.
Zuko reluctantly agreed to let Azula be the Alpha when she defended them in an uncontrolled animal.
Mai and Ty Lee were always scented by Azula, and Zuko never had the courage to ask for it too.
Zuko accepted that he would never have Mai when he saw a mark on her neck.
No one in the pack knew that Azula was studying how to be a good Alpha, much less that it was Lu ten who was teaching her.
When everyone left for the first time, Azula immediately shut down.
When everyone was back together they noticed how Azula surreptitiously perfumed them with her pheromones.
They noticed how Azula was ready to be abandoned again, they didn't know what to think.
Ironically, they weren't the ones who broke the pack bond, and it was the first time they felt the same way Azula did.