The X-Factor judges, who often go head-to-head in the style stakes, are believed to have bonded after what has been an eventful year for them both.
Singer Cheryl, 27, divorced footballer Ashley Cole amid rumours of infidelity, and was left fighting for her life after being struck down with malaria. And Dannii, 39, welcomed the arrival of baby Ethan with partner Kris Smith.
A source told the Metro newspaper that they've even opened the border between their neighbouring dressing rooms.
"It's the closest Dannii and Cheryl has ever been," the insider said. "In the past they've had little contact off camera. This year they have each other's number and are actually texting each other."
Cheryl is said to have been impressed Dannii's skills at juggling motherhood, working, and looking good.