She slept on filthy floorboards in a bare room, from where she dominated her parents and her brother, Russell, so much that when she died aged 29 they decided to join her in death. But their suicide pact failed.
Schoolfriends, neighbours, relatives - even her father and brother - had all been shunned when the shutters came down inside Karen's mind. A bucket used as a toilet became her only furniture.
By the time of her death in April, her self-isolation was nearly complete. For the previous eight years she had seen only her mother, and even then she ordered the older woman around with hand-written notes.
Her bizarre life and death - from bronchial pneumonia caused by a cancerous brain tumour - were described at the inquest into her death at Croydon Coroner's Court, south-east London, yesterday.
Paul Rose, the coroner, who recorded a verdict of death by natural causes, said the case raised some questions of the power of social service departments, but admitted it was unique in his experience and "totally bizarre".
Detective Inspector Robert Harrall said that from the age of 12 Karen had undergone psychiatric treatment but found staying in hospitals so unpleasant that when she returned home she would strip off her clothes and anything else associated with the institutions.
When she reached 15, her parents, Bob and Josie Morgan, were told that hospital treatment was no longer appropriate. Rather than lose her to a residential school, they decided to look after her at home in Erith, Kent. From that point, though she had resumed school, Karen's life began to take on its hermit-like pattern.
Det Insp Harrall said she "manipulated and dominated" her parents, for example over which television programmes the family watched. Ritualised washing which could last for hours was interspersed with periods when she refused to clean herself. Callers to the home, including neighbours, were either "ignored or turned away", he said.
For the last eight years of her life not even her father and brother - who also became a recluse - saw her. All her furniture was removed and she used the bucket as a toilet. Meals were put in her room only when she gave her mother permission.
Det Insp Harrall said officers had found "page after page" of notes written by Karen to her mother. If Mrs Morgan refused a command, there would be "tantrums and screaming and shouting sessions".
The family told no one when she died on 30 April, Det Insp Harrall said, and for three days Karen's body lay in the house, cleaned up, while Mrs Morgan worked as a cleaner to buy enough pills for them all to commit suicide.
Russell, a "willing partner" in the suicide, went first, but after feeling sick his parents called an ambulance whose crew was then told of Karen's death.
When Karen's body was examined her muscles were wasted, her toes clenched pointing down and her left leg bent. It would have been impossible for her to walk, but she had been reasonably well-nourished.
The policeman said the parents had felt overwhelmed by the situation, and, however "inexcusably", they had felt they were "protecting" their daughter. Any neglect, he said, was "self-imposed" and Karen was not an unwilling "detainee" in her room, which had no lock. There was no explanation as to what caused her condition.
Delivering his verdict, Mr Rose, said: "The whole history of this case is totally bizarre and unique in my experience. The deceased decided to live like a recluse, like some medieval monk deciding to live in a cell."
Karen had a "strange personality" and her parents had been unable to stand up to their daughter and report the situation to the authorities. Her death was not linked to her strange lifestyle, he said.
However, Mr Rose said he was "worried" that Bexley social services, despite taking legal advice, had been unable to act because there was no neglect or ill-treatment. No one had visited her since she was 15.
Mr Rose recommended that thought be given to whether social services' powers should be increased so that they intervene in such situations.
Mr and Mrs Morgan were not present at the hearing, which was told they had been treated with Russell at Bexley Hospital because of fears for their mental states. The parents were due to be discharged soon.
A spokesman for Bexley council, whose social services department carried out an inquiry, said they had offered help when Karen was 15 but the parents declined, and Karen had seemed to settle. There had been "no way of knowing" of Karen's isolation, and no one from the community had come forward. Updates in procedure had since improved, he added.
Dr Bridget Dolan, a psychologist at St George's Medical School, in south- west London, said there were a few cases of people shutting themselves away and starving to death. "The surprise is they don't happen more often. People fall through the nets all the time but we are trying to block the holes."Reuse content