YES I HAVE RETURNED AHAHA!
Go ahead and read, we'll talk at the end:

Months Later:

Aria-

Korra's bending has been restored with the help of her previous Avatar incarnations. Using energy bending she has been able to restore Lin Bei Fong's earthbending! Unfortunately we do not have the time to come all the way over to the fire kingdom to visit you but we are returning to Republic City soon and if you meet us there everything can be restored.
Looking forward to your master ceremony!

-Uncle Tenzin

Aria's mother Yuna found the scroll amongst others delivered to their isolated house by hawk. After much deliberation, she threw it into the fireplace where it was consumed by flames. Then she began a new scroll to write.
Uncle-

I am sorry, but I have decided to stay in the Fire Nation with my mother. She and my father were never benders, and I think with her help I will be able to manage and start anew here.

Kind regards,

-Aria

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As Tenzin read the scroll he had received from Aria, he felt sad. Although he knew with a bit more training Aria could regain her mastery and become a fully trained Airbender, he had to respect her decision to stay at home. He did not think to contact Bolin about the letter.

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Aria sat meditating on the practice field where her great uncle Sokka and her father Bumi had once been trained in the art of swordsmanship.
"Ari, dear! Come up and have some tea with me!" her mother called.

She rose silently and walked up the stone steps to join her mother on the veranda. Taking the tea, she waited for it to cool so as not to see the swirling curls of steam rising off of it.
"How about you and I go down to the village today and look at the marketplace? You've barely left the house since you got here two months ago dear." Yuna said.

Aria avoided eye contact, "I'm alright here. You go without me."

"Very well, my dear."

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Aria had taken to lying in bed long after she awoke in the morning. Not really doing much of anything. From time to time she would find herself thinking about what Bolin might be doing right at that moment but she would quickly shake the thought away.

I just hope he finds someone he can be happy with; someone who isn't broken like me.

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Months and months had gone by, and Aria was spiraling into a darker and darker state of mind. Her mother did not know how to help her. Aria had had next to no social contact since she had arrived home from Republic City. She even avoided her old companion Eero, giving him his food and water but never staying near him for long. This left her alone with her thoughts, which was not a good place to be.

She had taken to climbing to the very topmost roof of the villa and watching the sky. However as the weeks wore on, she began looking more at the ground.

You could fly, said a small voice in her head, even just for a little while.

Every day she went up there the voice in her head grew stronger and bolder.

Don't you want to feel the wind in your face?

You could leave this world feeling as if you'd gotten your bending back.

Finally one day, she listened to the voice.

Standing up, she felt the wind pushing her towards the edge of the roof. She eased forward, eyes on the ground. In a second, her feet were off the roof and she was flying…

I'm finally flying… Aria thought as she fell, feeling the wind whistling around her as time seemed to slow.

"ARIA!" her mother screamed as she saw Aria plummeting towards the earth.

In a flash of cream and brown, Eero had caught her on his back. He brought her down to the ground and her mother ran over to her, tears streaming down her face.
"Aria! Aria are you alright? What happened?! Did the wind push you?"
You could say that… Aria thought. Although winded from the landing on Eero's back, she managed to climb down to her mother.

"I'm ok mom." Aria said quietly and turned to walk back into the house.

"Aria you stop right there," her mom said sternly, "Did you… did you jump off the roof?"

"Yeah, so?" Aria said, still facing away from her mother.

"Were you trying to kill yourself!?" Yuna said, her voice raising.

Aria spun to face her mother, "Yes, I was!" she snapped. "Do you have any idea what it's like to lose a part of your soul?! What its like to be stripped of your identity and not be able to love yourself much less any other person?! Because that's what I live with every day!"

Yuna began to cry, "this is all my fault…" she whispered.

Aria softened, "Mom, no it isn't your fault, its that bastard who took away my bending."
"You don't understand…" Yuna said with a sob, "It is my fault. Not long after you got home, I received a message from your uncle and father at the south pole."

"What are you saying?"

"The Avatar was able to regain her bending due to her connection with her past incarnations. Using their knowledge of energy bending… she has restored the bending of those who had theirs taken away by the waterbender Amon," Yuna said, ashamed of herself.

Aria was speechless.
Yuna looked down as the tears fell, hugging her arms around herself, "I just… your father and I don't have any bending and, though I know it was a dream come true for your father when we found out you could bend, for me it was… well it wasn't the easiest thing."

"But why did you keep this from me?!"
"I wanted to have a non-bending daughter! I was selfish, and I know that! But I wanted to be able to have you here with me instead of off with your uncle and your bending… Please forgive me, please my darling Aria…"

Aria was experiencing an emotional whirlwind; excitement at the prospect of getting back her bending, anger at her mother, disappointment in herself. She hugged her mother.
"I don't forgive you yet, but I… I can see how you thought it may have been best for you."
Her mother continued to cry.
"But you know this means I can't stay here any longer. I have to return to Republic City."
"I know," Yuna said, "And I know you will be the best airbender since your grandfather."

SO, if you can't tell from my own little deus ex machina, I really disliked Book 2. First of all I think the series would've been much more interesting if Korra had had to earn back her bending! Like, if she had spent a good part of season two as just an airbender and through her training in the spiritual side of being the avatar she would regain her bending and be able to fix other peoples. Because seriously how can you energy bend and NOT be a spiritual master? And yet after Korra energy bends back folks' bending, she has to go through serious spiritual training. I also really disliked how once again as in Book 1, Bolin's romantic pains were treated as comedy. His and Eska's relationship was straight up abusive. If the show had done the same kinds of things with a male character in Eska's position and a female character in Bolin's, there would be outrage online for showing an abusive relationship for laughs. Yet there was not with Eska and Bolin. Not only that but Eska and her brother… great characters, but terribly treated by other characters. Their social ineptitude (which I'd say would likely fall somewhere on the autism spectrum) was a joke. I loved Eska in general, her voice actress is golden of course, and she is a very strong-willed and powerful bender.
Ok, so now I'd like to formally apologize for making all of you, my amazing dedicated readers, wait so damn long for this chapter. College is rough and tough and I've had a lot of stuff going on including failing a couple classes and subsequently switching majors this fall. I also got a boyfriend who I adore and is perfect! Aaaaaaand probably of no surprise to any of you he is a ton like Bolin in personality lol! But now that I've switched majors and have got some better tactics for how to stay on top of my more difficult and boring classes I think I'm gonna be better. Also this summer I am doing an internship in a part of the country where I have no internet except at work so that obviously gives me a lot of time to write!
ALSO I have not seen ANY of Book 3 (a consequence of no internet…) so I won't be writing a TON because I don't know whats going on in the canon :P