Here is a review for ninawolf_

My comments will be in bold

Basics and grounding

The first avatar oc I've reviewed so this should be fun.

Character information

These are all fine but I think maybe work on that personality a bit more. Maybe try to balance out the traits some more because she seems to have a personality that comes across as pretty negative.

Mainly work on her description because I don't know anything like her skin colour, body type, face shape, ect. So add a lot more detail to that.

Relationships

Alright so you gotta add more detail to these and flesh them out. Develop them more. I feel like she would at least know her fathers name by the time she's sixteen but you have mentioned a difficult relationship with her mother. As far as friends go, I normally suggest designing some kind of oc to be her friend aswell when the cast is pretty small and also not to make her friends with everyone, it can be unrealistic.

This is the first time you've brushed on the airbender aspect of things and I'll talk about that later.

Backstory

Alright I'm going to address the airbending because whilst this could work, it completely disregards a large chunk of the plot of Aang coming to terms with being the last aitbender, I mean, it's literally in the title of the show. You could easily change the story slightly and make them earthbenders instead but if you want to keep it the way it is then it's not my place to stop you.

The other main issue is with the fire bender looking after her grandmother. She would easily be found and slaughtered due to the nature of the fire nation. We see them do patrols several times in the show itself and raid people's house when they're even just common benders.

You need to figure out the logic and reasons behind all of this and rethink it. Make it work.

Other

Alright this works to an extent but my previous points still apply because this could be done with any bending ability.

Stats

Stats are balanced this is fine.

Final thoughts
Overall, I think you need to look at this from a more logical point of view and make this character's transition into the universe make more sense and work better, especially regarding her abilities and relationship with the fire nation.

*My critiques are simply at your request and to help improve your character. It is not my intention to cause any offence and you, of course, do not have to listen to what I've said. This is all just a bit of fun and I apologise if I have done any kind of damage*