Stacey Worsley's deception eventually came to light after police were tipped off by the UK Gambling Commission.
Suspicions were raised in November 2017 when it became clear that she had access to large amounts of money and had suffered "significant losses" over a short amount of time.
Phillip Adams, prosecuting, told Leeds Crown Court that the offending was in relation to the mismanagement of money which was for the treatment of Worsley's son, Toby Nye.
Toby was diagnosed with neuroblastoma, a rare form of cancer, when he was aged four.
He was given a course of treatment on the NHS which failed and Toby's family were faced with starting a funding campaign to raise £200,000 to pay for further treatment.
Worsley's mother set up a JustGiving crowdfunding page in February 2017 which contained a link enabling people to pay directly into a bank account.
Mr Adams said money was also raised through events such as charity balls and raffles.
A donation of £2,000 came from a woman she had built up a friendship with at Leeds General Infirmary.
Another woman at the hospital had raised £5,000 for her own daughter who had cancer.
The woman donated the money to Toby's fund after being told she would be receiving NHS funding for her daughter's treatment.
Toby's primary school became involved in fundraising, transferring £5,000 into Worsley's bank account in August 2017.
Leeds United became involved in August 2017 when the club's staff and owner Andrea Radrizzani became aware of Toby's plight.
Mr Adams said: "They (Leeds United) gave an undertaking to the family that the funds would be met by the club."
The football club continued to promote the JustGiving page, beginning their involvement at a game at Elland Road against Sheffield United in 2017.
Players and staff also contributed a day's wages as part of the appeal.
By November 2017 the amount raised stood at £65,000.
Mr Adams said because of the commitment from Leeds United it was decided to close the JustGiving page down.
A sum of £24,000 was transferred to Leeds United and the balance of £41,573 was transferred to Worsley's bank account.
Mr Adams said it was agreed that the money was to be use to "enhance" Toby's life by paying for experiences.
Worsley continued to receive further amounts into her bank account from fundraisers.
The £200,000 target was reached in January 2018 and Toby received his treatment throughout spring and summer of that year.
Mr Adams said: "All of the money raised by the club went towards Toby's treatment."
Worsley was arrested and interviewed in January 2018 in the presence of a solicitor but refused to comment.
An investigation was launched and found that £59,145 had been paid directly into two of her bank accounts, in addition to the £41,573 that had been paid from the JustGiving account closure.
Further amounts had also been paid into her account from family and friends.
Mr Adams said: "Over the period she lost approximately £140,000 to online gaming companies.
The investigation showed she had online gambling accounts which dated back to 2009, 2012, 2015.
The prosecutor said: "It's true to say that the defendant stopped gambling following her arrest."
The court heard that the online gambling companies have paid back £135,000 which was lost by Worsley and the money is currently sitting in a West Yorkshire Police bank account.
Worsley pleaded guilty to fraud on the basis that she had taken £100,000.
The basis was accepted by the Crown Prosecution Service.