I think she is prickly, she's fussy, she;s petty as hell.... It could be she is supposed to be annoying and melodramatic. Like a foil/parallel for Zuko. A girl who is melodramatic and brooding for dumb reasons who then is forced into real chaos and trauma. So she has to grow up and realize her inner strength doesn't come from how much you suffer, but how much you maintainyour good attitude in the face of suffering.
So when paired with someone genuinely struggling her offbeat but sincere attempts to try to have compassion for him make her the brave confident person she wants to be.
The only thing I like about is her fighting style, her nails, and her eyes. That's pretty much it. I'm not a big fan of moody characters that are the walking and talking defintion of pessimistic. Her rocky relationship with Zuko doesn't help things. And poor Kei Lo is just the victim of Mai in rebound.
I would say she is okay-ish...the only thing I really hate about her is the way she treats Zuko. He wants to tell her his worries and all that stuff and she just says : "I didnt ask for your entire life story", she doesnt really make a good girlfriend