In reply to Paulo.

Google it. On the 2017 Grammy's red carpert she made a joke about the head shaving incident. She also posted a shady magazine article on instagram which said Britney is only handed a script and has never had creative control over her career. Her manager also tried to fix this by telling fans to request "Slumber Party" on the radio instead of coming after Katy (shady because slumber party wasn't doing well at radio).

She said something else too, but she went after Britney and never acknowledged.

A quick google search will show everything. Katy is a b*tch and this is her karma