Martin Short has spoken out following the death of his daughter, Katherine Short, who died in February. She was 42. “It’s been a nightmare for the family,” Short told CBS Sunday Morning of Katherine’s death. “But the understanding [is] that mental health and cancer, like my wife’s, are both diseases, and sometimes with diseases they are terminal. And my daughter fought for a long time with extreme mental health, borderline personality disorder, other things, and did the best she couldn’t until she couldn’t.” Katherine, the eldest of three children adopted by Short and his late wife, Nancy Dolman, died of a self-inflicted gunshot wound, according to the Los Angeles coroner. Popular on Variety A licensed social worker in Los Angeles, Katherine dedicated her career to mental health advocacy, working with the charity Bring Change 2 Mind, which focuses on reducing stigma around mental illness.…