Mary Ellen Field arrives at the high court today to give evidence to the Leveson inquiryCredit: Sean Dempsey/PA
Mary-Ellen Field advised Macpherson on her finances and became a friend and confidant, she told the inquiry.
She added that the working relationship was "very successful for both of us, both financially and from a developmental point of view, we did lots of exciting things".
But she was later accused by Macpherson and her employer Chiltern of being an alcoholic and leaking information about the model to the press. She was "bullied" into attending rehab, she said, and then made redundant in March 2006, leading to a bout of ill-health and financial strain.
The redundancy came with no warning, according to her testimony, and she maintains that the move came as a direct result of the situation with Macpherson.
Macpherson's was identified by the police in 2006 as a possible victim of phone hacking, but unlike many other public figures has not undertaken legal action against News International or spoken publicly about the scandal.
Several reports have suggested that she made a secret out-of-court settlement with the publisher, a claim denied by her lawyer and publicist.
Field is pursuing a civil litigation against News International, which she told the court she was able to do thanks to a CFA, or "no-win-no-fee" agreement.
"I couldn't afford it otherwise," she told the court.
Concerned in 2004 about how information was being obtained by the press, Field arranged to have Macpherson's house and phones swept for bugs by a security firm.
She told the inquiry that the firm didn't find anything, "but now we know that wasn't how they were getting the messages".
After hearing about the arrests of Clive Goodman and Glenn Mulcaire in 2006, and that MacPherson had been named among the possible victims, Field contacted the police to report her story.
She told the inquiry today that she was ignored by the force, despite phoning Scotland Yard and writing twice to the then-commissioner Sir Ian Blair.
Nothing happened after that, Field said, until she read the Guardian's 2009 coverage of the scandal and tried to reach the reporter who broke the story, Nick Davies.
Instead, she spoke to Stephen Brook who invited her to the newspaper's offices to do a video interview about her experience.
Field also assisted the New York Times with its 2009/10 investigation into phone hacking, and has been interviewed by the BBC.
Her civil suit against News International is ongoing.
Field is one of four witnesses scheduled to appear today, including actor Steve Coogan who is due to give evidence this afternoon.