Mrs Diprose said Kate had always enjoyed art and it was a nice way for her to relax between treatments.
"She'd asked for an easel for her birthday because she likes painting. So we got her an art box that turns into an easel so we can take everything with us."
The Starship storybook, Home Sweet Home & Seven Hearty Tales, features the work of eight student authors aged 7 to 13. All the proceeds from its sales will go to the Starship Foundation.
Among the artists are All Black Keven Mealamu, netball star Anna Harrison, painter Tracey Van Lent, Japanese artist Jun Arita and designer/artist Erika Pearce.
The stories, chosen from more than 1100, share the theme of the importance of family and belonging.
Kate illustrated "Spotty's New Home" by Caleb Palmer from Elim Christian College, a story about an abandoned dog and a prince in a castle.
Kate loves dogs and said she based the story's main character on a familiar face: "My brother's black and white springer spaniel."
Mrs Diprose said it took Kate a solid two or three days, stretched over a few weeks, to finish the illustrations.
"We did them in starts and stops because Kate at the time was recovering from pretty major side effects. She'd had eight really strong doses of chemo and she had chemical burns on her eyes ... "
When asked what she liked most about art, Kate said: "The pictures I get to create." And what about this book project? "It's just cool," she said.
When asked to describe the whole experience in one word Kate paused, and with a big smile whispered: "Exciting."
This year's supreme winner was Josephine Sim, 7, from Cockle Bay School with her story "Home Sweet Home", illustrated by Mealamu.
It featured on the cover.
The humble All Blacks veteran said it was "a real honour" to be a part of the project. "The money we are able to raise for Starship - it's really nice to be able to do something nice like that.
"We're very lucky to have some very talented children - the authors - and it was a real honour to be able to have some illustrations next to the artists that we have here."
Mealamu put the finishing touches on his illustrations in between playing at the Rugby World Cup in England and said it provided him with an escape. "It's something that I've always loved to do."