Mary Cosby Becomes Emotional on 'RHOSLC' Over Son's Death

Mary Cosby went back to work pretty soon after her son, Robert Cosby Jr., passed away ... and she's now revealing she had to compartmentalize her life to get through it.

The new season of "The Real Housewives of Salt Lake City" is out now ... and fans are seeing Mary deal with Robert's shocking death ... with a new scene showing her just two weeks after his "homegoing."

Mary says she's in "survival mode" ... forcing herself to only think about Robert briefly -- and not allowing her grief to consume her.

Angie Katsanevas also makes an appearance in the clip ... saying she's missed Mary because she's not trying to overwhelm her during that time. The two then talk about Robert.

We broke the story ... Robert died in Utah back in February, a few weeks after he was charged with felony domestic violence.

Dispatch audio revealed Narcan -- a nasal spray that counteracts the effects of an opioid overdose -- was administered to Robert before his death.