And then Saturday came, and Katy performed at the rally -- she sang "Firework" and even called Clinton her firework, after Bill Clinton was her self-described "opening act," as per ABC News -- dressed in a patriotic display of support.
In addition to appearing at the rally and lending her vocal cords, Katy took over Clinton's Instagram account for the day, showing off her Clinton-centric swag and giving her a chance to connect with even more folks via social media. Here's what we learned from a KP takeover.
Katy's nails vote Democrat.
"The stage is set, and the nails are pressed. ? T-minus 1.5 hours before we Roar together. #ImWithHer," she wrote on Insta.
And it runs in her family.
"I'm here in Iowa, but meanwhile back at home, my niece… #itrunsinthefamily."
She also likes to meet fellow supporters.
"Supporting a supporter, Noah from Iowa. #volunteer #getinvolved."
And take on-point selfies with the lady of the hour.
Of course, she knows how to bring her A game when it comes to birthdays.
"My birthday gift to fellow Scorpio, Hillary, says it all. ♏️ "
For the record, Clinton's birthday is Monday, Oct. 26 -- while Katy's is today. So, happy birthday, Katy! Have a great one...even if it's stressing you out.