I say at least 5..... Maybe 10....

Well, she was 8 years old in Zuko Alone and already on the path to evil, which means the past 7 years were building her up to it. Thus I'd say, along with the obviously-needed presence of her mother, a good new 7 years...in short, the rest of her teenage life.

"I think she is beyond therapy."

So is the Joker, that doesn't stop the Arkham staff from trying to give it to him.

Yeah, and the Joker busted out of jail repeatedly and killed dozens of people.

I think the only way she could heal is her mother, and that is a far, far stretch.

Remember what Ursa (Azula's hallucination of her) said in the finale;

Ursa: "You're not a monster Azula... you're confused. All you're life you've used fear to control the people around you... like those friends of yours; Mai and Ty Lee"

Azula: "Well what other choice do I have?!!! Trust is for fools - fear is the only reliable way" *glares at mirror* "Even you fear me".

Ursa: "I don't fear you Azula; I love you".

Azula: *trembles for a moment and then screams and smashes mirror with a hairbrush before collapsing on the ground, sobbing*.

Deep down, Azula always knew that her mother loved; she just couldn't bring herself to accept it, and still can't. Once she accepts that her mother does love her it will go a long way to helping her, but she'll also have to learn to love her back. Azula's chief problem is that even though she would dearly like to feel some love for other people, she has no idea how to do it. If she were to find Ursa, and ursa were to help her see how to return love, she may well be capable of starting a new life.