The 40-year-old actress, who has four children, Liam, six, Stella, five, Hattie, two, and 15-month-old Finn, with her husband of seven years, is completely devastated, reported People magazine.
The former 'Beverly Hills 90210' star is focusing on her kids.
"She's much more heartbroken than anyone realised. She's flipping out and is completely devastated," a source said.
McDermott, 47, was accused of having an affair with a woman he met in Toronto before Christmas but Spelling has yet to publicly address rumours their marriage is on the rocks.