Katherine Short's Friend Says She Was a Beautiful Soul, Carried Weight of World

Katherine Short -- the late daughter of Hollywood legend Martin Short -- was a "beautiful empathetic soul" who "took on the baggage of the world" as a mental health worker ... a close friend of hers tells TMZ.

We broke the story ... Katherine died by suicide Monday inside her Hollywood Hills home. Law enforcement sources told us she died from a self-inflicted gunshot wound.

Katherine was a social worker and worked for a mental health nonprofit ... and her close friend told us her work weighed her down. We're told Katherine was laser-focused on hearing other people's problems that were being thrown at her, and she was always trying to help them with their mental struggles, which she could relate to.

Katherine's friend tells us she did not readily discuss her own specific mental health problems ... other than to make it clear she had them.

We told you Katherine had a service dog, Joni, to assist with "mental illness" ... and the friend says she had another dog before ... a rescue named Charlie who was "loving and comforting to her and made her feel safe."

Katherine wasn't a solitary person. We're told she had friends ... and the last time she spoke with this close friend, nothing in their conversation indicated anything impending.

One last thing ... the friend knew Katherine as Katherine Hartley -- her middle name, not her famous last name -- and says she didn't go about broadcasting she was the daughter of a Hollywood star.