Even being of the pro-Fatina faction, there are plenty of redeeming factors about Kaaya. Granted, most of them are in the first season where she was more prominently featured.Originally Posted by Archangel
(It's a trade off, she was hotter in the second season solely due to costume and styling choices. Or rather we actually discovered how attractive she really is.)
While she was certainly rather subdued due to the gravity of the task before her and considering her lineage, Kaaya's real personality does seem to be more in line with her grandmother. She too lies and plays tricks on others for her own slightly sadistic enjoyment. Fatina is a lot more straightforward, serious, and seems to greatly dislike lying to anyone other than herself.
Kaaya, when not worried about killing her own grandfather, is a bit more of the chipper or "genki" character type. My personal favorite part about Kaaya in the first season was where she lied to Jil, multiple times, about how terribly sick she was so that she might essentially torture him playing the original Druaga Arcade game in order to get treasure.
She's a lot more mischievous than Fatina, and that's a pretty attractive character trait in a girl, in anime or in real life.