Performing, music, innovation, etc. They are spiritually bonded, it's not like she has to deliberately do things to draw comparisons—it happens naturally.
Katy's had a massive career. Her legacy is undeniable.
Her "legacy"? The only issue is that her music is, for the most part, meaningless pop music.
I'm not saying most of my faves are meaningful pop but I can find more substance on a K$ record.