Katy's a heavy self promoter. She mentioned her song a few times, that she wrote because of the difficult place she is in her life (playing the sympathy card for the divorce). Her performance was later on in the show, and it was more theatrical and thus memorable, even though the vocals were atrocious.
I still love Katy and her music though

She's just a ditsy, less talented, and over-sexual version of what Kelly would be like if she was a sell-out. And while those things sound mean to say, I challenge anyone to point out a single one that isn't true.
Back on the topic of Kelly. Dancing with the stars tonight!!!