The actress, who famously split from Brad Pitt in 2005, is said to have comforted the Indecent Proposal star during the Christmas period and offered the use of her yoga instructor Mandy Ingber and her private chefs Jewels and Jill Elmore.
"Jen knows better than anyone what it's like to have a break-up in the public eye," a friend told Now magazine.
"Demi feels publicly humiliated and Jen can totally empathise. She's read every self-help book out there and helped Demi compose the announcement of her split."
The two actresses apparently became friends when they co-directed Five, a series of short films about breast cancer for the Lifetime network.
Moore announced her split from Kutcher in November last year, following claims the Two and a Half Men actor had cheated on her.