You clearly no nothing about music if you think she can't sing or her music is written for children She's the best popstar of this generation. And since you really asked what makes her music better than Katy Perry, it proves your a troll and should not be on a music forum.
First of all, her persona is really fake and just overall vile. And as if that wasn't enough, her musical qualities ain't much better. She's got a terribly weak voice, her songwriting is trash and she can't dance to save her life. I don't get her appeal AT ALL.