I think what keeps Kitty from becoming absolute Sue is the fact that we don't get to hear her speech about why Chris can't get laid. If she were an actual Sue, her every word would be worthy of record. What she's saying here is something that's been said many times before.

When Chris becomes infatuated with Kitty, it isn't meant to build her up a sex goddess or anything (I am not a furry), because honestly, Chris' opinion isn't worth a lot. It's actually a parody of how he misinterpreted his relationship with Vivian and tried to get with her even as she was torturing him.