Shelley Tomes was found guilty on Tuesday at Highbury Corner Magistrates' Court of three counts of fraud by false representation against her former employer, music and entertainment agency The Cult PR.
Tomes worked as a partner at The Cult PR between June and September 2010, during which time she defrauded £4,600 from the agency.
The case has now been sent for pre-sentence reports and Tomes will return to court on 27 September to hear sentence passed.
Tomes told PRWeek: 'Obviously this decision did not come lightly. However, this has been a long drawn-out year and, at this stage, I feel far too much time and energy has been wasted and taken away from my main priority - my clients. All of whom, along with friends, family and the industry as a whole, I would like to give my unreserved gratitude to for their unwavering support and belief.'
She now runs her own agency Fresh Milk PR, which works for Creation Records founder and the man who discovered Oasis, Alan McGee.
Tomes added: 'It is now time to move forward. I would also like to wish The Cult PR the very best of luck for the future.'
The defendant failed to attend court in a series of no-shows, in which she cited 'depression and anxiety'.
Tomes has recently been appointed to work for McGee internationally, and is now managing artists as well as handling PR.
The Cult PR co-founder Matt Glass said: 'We trusted a friend and gave her the opportunity to further her career as part of a well-respected PR company. Unfortunately, Tomes used that opportunity to fraudulently take money from our company.
'For the past year, she has denied any wrongdoing but, on the eve of the fourth scheduled court hearing, has finally accepted she is guilty.'