I'm guessing she doesn't follow charts, I don't think anyone can seriously accuse Katys singles of plummeting quickly... Dark Horse is still Top 6 6 months after being released.
To be honest, I don't see the shade but I guess Christina Perri does not follow charts as unlike she said, Katy Perry's singles do not plummet quickly.
i think she just meant that those songs get radio support as soon as they're announced as singles, become hits for the artist and then dropped for the next single that artist releases. whereas her songs pick up support slowly