He suggested she "should be doing [it] often, for self-pleasure", and to "make [her] smile", she said.
The doctor had also recommended "therapeutic use of sexual behaviours", low pressure water enemas, and deep abdominal massage as treatment for the her bulimia.
The doctor had also prescribed the woman with medication over a number of years despite "known risk factors" and an accidental overdose.
In particular, Mr Hill said the continued prescribing of zopiclone, a drug usually given to insomniacs, was "unsafe, poor practice, and put [the woman] at risk of harm".
The GP was found to have breached the Code of Health and Disability Services Consumers' Rights in a number of respects, and aspects of his treatment were found to be "not clinically appropriate".
In particular, the doctor's recommendation of enemas and abdominal massage were not supported by medical literature, and had the potential to reinforce the focus of the woman's eating disorder, Mr Hill said.
His repeated discussion of masturbation and inappropriate comments to the woman were a breach of sexual boundaries, Mr Hill said, and he had behaved in a manner which breached the doctor-patient relationship of trust.
The GP "showed a lack of judgment by recommending strategies that were beyond his expertise", Mr Hill said, adding the doctor should have referred the woman to a specialist health provider.
The doctor was ordered to undergo a competence review by the Medical Council, and remain in a mentoring relationship with two senior colleagues.
He has since written a letter of apology to the woman.
