MARIE OSMOND has been shattered by the death of the man she called her “second dad,” and friends fear Marie could be breaking down!

A source says the Nov. 23 passing of “Pap” – her best friend’s father, 78-year-old Richard Roman – has Marie, 54, down in the dumps.

“Marie is fragile around the holidays – she’s been that way since losing her son Michael,” a source told The ENQUIRER. “She just can’t handle the death of another person that close to her, especially at this time of year.”

Michael committed suicide at age 18 in 2010, and it nearly drove a depressed Marie into a mental institution, said the source.

“Since Pap’s death, those close to Marie have noticed the same symptoms – lack of sleep, weeping, anxiety,” from when Michael died, said the source. “We’re all worried sick about her.”

After Marie’s beloved father George Virl Osmond died in 2007, she began turning to Pap for fatherly advice. And when Pap passed on, Marie wrote on Twitter: “My girlfriend of 44 years, Patty, lost her dad. He was a second dad to me. Praying for her and Mom.”

Marie couldn’t attend Roman’s funeral on Nov. 25 due to rehearsals for her Christmas tour with brother Donny, and that only added to her heartbreak, said the source. But with the Christmas tour’s success and her fifth year of shows with Donny at the Flamingo in Las Vegas kicking off Jan. 14, Marie seems to be fighting through her pain, said the source.

“As long as she’s working, Marie doesn’t have the time to dwell on Pap’s death,” a pal told The ENQUIRER. “Besides that, she’ll soon be a first-time grandmother, and that’s sure to help her to get through this difficult time.”