A Melbourne mother who stole $8 million from her employer suffers a multiple personality disorder and one of her 10 personalities was responsible for her actions, a court has heard.

Wendy Hope Jobson, 50, of Leopold, stole $7.8 million while employed as an administrative manager with the Koroneos Group, which owns and manages hotels in Geelong and Melbourne.

In 1478 unauthorised transactions she siphoned money from company accounts to her personal accounts, falsifying invoices to cover her tracks between 2006 and 2011.

She spent millions on online gambling sites and purchases, including a $40,000 car and a corporate box at Etihad Stadium.

Jobson pleaded guilty in the Victorian Supreme Court on Monday to six charges of theft.

Her lawyer Michael Stanton said Jobson was suffering a multiple personality condition called dissociative identity disorder (DID) which impaired her ability to make rational judgments.

Jobson's psychiatrist Dr Sylvia Solinski said DID was a disorder where a person could switch, involuntarily, automatically and wholeheartedly to another person, likening it to an "out of body experience".

Sufferers could be "out of touch with reality" and experienced amnesia, she said.

Dr Solinski said she had identified at least 10 personalities within Jobson, including one named Reggie.

"Reggie has been most prevalent," she said.

"She's the one who is most common and has identified herself to me to be present to protect Ms Jobson in a range of systems, in a range of ways."

Dr Solinski said Jobson did not have a gambling problem and the offending was her way of seeking attention and punishing her employer for perceived wrongs.

Crown prosecutor Peter Rose SC said reputable sections of the psychiatric field did not accept DID.

When he asked Dr Solinski whether part of Jobson would have understood her wrongdoing, she said: "Yes she would, and it would be Wendy."

Mr Stanton said the DID developed in Jobson's childhood after she became the target of school bullies who broke her arm.

She developed an imaginary "older brother" figure named Sam, he said.

Jobson was remanded in custody ahead of her sentencing on Tuesday.