Halko was a medical physicist, and was on the staffs at Michael Reese Hospital and Cook County Hospital, both in Chicago. She was Clinical Assistant Professor of Radiology at the University of Illinois College of Medicine. Her research was published in academic journals. She was the first lesbian president of Dignity/Chicago, an organization of gay Catholics. In 1985 she co-founded Chicago House, a social service agency assisting people with HIV/AIDS who needed housing, hospice care, and other supports. From 1982 to 1989, she was a co-owner of Piggens Pub, a lesbian bar. In 2000, she and fellow activist Marie J. Kuda co-founded the Jeannette Howard Foster Memorial Sewing Circle and Book Club, dedicated to preserving Chicago lesbian history.