Azula in a Fire Nation witch outfit!? Cute!
Actually, the Blue Spirit is Zuko in disguise so technically, this is more like a Azula-Zuko sibling art because she is hugging her brother, even though she does not know the Blue Spirit's true identity.
Therefore, they're having a 'sibling love' time. No, not Zucest! Never crossed in my mind! Never!
And I think I know why the Blue Spirit/Zuko has some sweat drops on his head.
This is maybe because he feels awkward that he was hugged by his own "evil, ruthless and scary" little sister who actually (I'm not sure) is a big fan of his alter-ego.
At least in this art.