The celebrity was inundated with requests on Twitter to 'Roar for Jess' – the young Harefield Primary School schoolgirl who has been fighting a rare childhood cancer on and off since she was three.
And the pleas were heard because on Saturday Ms Perry tweeted directly to Jess's campaign page on Twitter that she would be singing 'Roar' for Jess that night.
A delighted Jess published a video in response thanking Ms Perry, who is one of her favourite singers. See below.
I ? you, @RoarForJess, and I ❤ you, and I’m singing this one for you tonight!— KATY PERRY (@katyperry) June 15, 2018
You have all been totally amazing and made it possible for our beautiful princess Jess to have one of her dreams come true tonight ♥️I say it again and again but we really love and appreciate you all more than you will ever know #LoveThisTwitterFamily ♥️♥️ pic.twitter.com/eCosvCzMiE— Help Jess Beat Boris (@RoarForJess) June 15, 2018
Hillingdon is Here first reported on Jess Shepherd in 2016 when she was eight. Her family were trying to raise funds for essential medical treatment in America that she could not get in England. There has been a huge campaign in Harefield and surrounding areas to raise money for Jess through a whole range of activities and events.
But in devastating news for all connected with the youngster, her family recently said on social media that they no longer have hope of a successful treatment. They said they are concentrating on giving Jess the best possible experiences from a wishlist of activities she wants to do with her brother and sister and building 'precious memories'.
Jess, who lives in Ruislip, has been fighting a rare childhood cancer on and off since she was three.
Although it went into remission spontaneously, it came back in December 2013.
She named her tumour Boris and thereafter the Help Jess Beat Boris campaign sprung into action.
Follow the Jess Twitter page for more information and the latest news.