I came to this thread while searching for information on Adrienne Johnston. Since then, I located an article in the Irish Independent from Dec. 16, 1989, which strongly implies that she was a victim of domestic violence. She apparently died in a fall at home; while the death was ruled accidental, the medical examiner expressed "concerns about this case" to a family member.
The article portrays Adrienne's husband, Chris McCloud (né Miethe), as controlling and opportunistic, hoping to ride the Johnstons' coattails to fame and fortune. During the last half-dozen years of Adrienne's life, her friends and family were unable to get in touch with her to let her know of the deaths of her parents and other relatives.
Very little information is findable about her husband, except for a posting from one of his high school classmates, who states that McCloud is "deceased (date unknown)". (http://web.me.com/davidgjnitz/Site_2/Obituaries.html)
I hope it doesn't seem too morbid of me to be digging up this information so many years later. I've always loved the Johnstons' music and have wanted to know more about the tragic loss of Adrienne. "Oh, but her love, t'was easy won."