I actually haven't really introduced Ai to RC, but a few know of her. If you don't know, she's Chen's probending teammate; the waterbender of the group.
She hasn't had much character development as of yet since i rarely bring her out, but there were a few things that I can list that are canon.
She's Chen's childhood friend and Chen's her childhood crush (still present)
Her infatuation for Chen is one of the influences of wanting to be a probender. (When she was a kid she even claimed to Chen that she'll one day be apart of his probending team. Chen, being a kid, said "NO WAY. GIRL'S AREN'T ALLOWED STUPID.)
As she gotten older, her innocent crush, became much more and much deeper. At the same time, Chen is oblivious to the signs which obviously frustrate her.
During or in between the three year time skip, a confession was made, but she didn't get the answer she was hoping for.
Head Canons:
Despite the times she had a thing for Chen, Shun had always came into view which brought confusion. At first she thought of him as an annoyance through his "flirty behavior" (not to her but to other women in general) and pretty much no interested in him since her eyes were only on Chen
BUT, as time goes on...Ai start to notice that Shun's not completely bad. Redeeming qualities starts to show, through interactions and times when she witness him in his "positive-state'' (she only views him as a pervert money-crazed evil dude lol)
I don't know whether she starts to become interested/attracted, because she's probably still recovering from Chen's rejection, but i feel there's a spark or that she's more aware of him after seeing that Shun's not a bad guy. She becomes less condescending and more open to the idea of of associating with him. ^^;