It was reportedly a flight to Darwin that aroused suspicion leading to an investigation into Harrison's expenses.
After an audit commissioned by Seven West Media into the expenses charged to the card was completed, the majority of the charges, A$358,173 ($390,500), were found to be legitimate.
The report concluded A$149,251 ($162,700) in expenses were likely personal and A$26,932 ($29, 360) required further investigation.
Harrison has reportedly accepted some of the charges were personal and agreed to pay them back.
But the fact that each expense listed in the report - including hypnotherapy and purchases from designer fashion labels Chanel and Sass & Bide - were initially approved and paid for by Seven, highlights the unusual level of trust and power handed to the once-trusted worker in her role as executive assistant.
In court documents, an email from Harrison shows she told a colleague that her boss, former Pacific Magazines CEO Nick Chan, was "very easy to ... get around".
"Figured it out day f***ing 5 if I'm honest," she reportedly wrote.
A former executive assistant who held roles reporting to Australian media executives told news.com.au the role of an EA came with power.
"I've always been trusted to make decisions for my bosses, on their behalf, and without their consultation," she said. "I have approved my own expenses on behalf of bosses, I've approved the expenses of employees for my bosses and also flagged with them things that they need to be aware of."
The former worker said she had been trusted to approve requests, manage finances and investments on her bosses' behalf.
"I once worked for an executive at a professional services firm who used to tell her staff that approval from me was always as good as approval from her," she said.
Another former EA told news.com.au it was not uncommon for assistants to make "unusual purchases".
"When you're a personal assistant you're given the highest level of trust so things like expenses aren't necessarily questioned," she said.
Among Harrison's more unusual reported expenses were multiple sessions with hypnotherapist at A$250 ($270) each, a Weight Watchers package costing A$3266 ($3560), and a A$4494 ($4900) bill from Dan Murphy's which was noted as being for the 2013 Christmas party, according to the AFR. Those expenses were all disputed in the report.
Harrison is unable to comment on the report under the conditions of a gag order imposed on the former employee by Seven.
The broadcaster made legal moves to gag Harrison after she went public with details about her affair with Seven West Media's CEO Tim Worner.
Harrison plans to fight the order in the Federal Court with the assistance of high-profile barrister Julian Burnside.
The once highly trusted assistant has become embroiled in a messy legal brawl with the broadcaster who she claims failed to fulfil a payment agreement after she was made redundant or dismissed.
Seven has denied leaking the Deloitte report.