As I am all too well aware. However, that doesnt mean Katara has to love Aang romantically. She isnt one-dimensional; she has a mind of her own. How would you feel if you had to get married to someone who loved you, and yet the feelings werent mutual? Talk about unhappy.
And as for Katara pitying himyes, I am aware of that as well, having, like I said, seen every single episode at least once. But pity love is not the same as romantic love. Romantic love is wife/husband. Pity love, however, is mother/children (alongside familial love). Again, referring to the Oedipal complex issue. Her personality is, on many web sites, considered to be the mother of the group. This mothering was often directed towards Aang. Hence pity love (which, in reality, is no love at all).