Janet French said Katy spent three days in St Vincent's Hospital in Dublin after she had allegedly been beaten across the head several times and kicked in the back and stomach.
Her worried mother later brought Katy to a garda station to make a report. However, the model "didn't want to press charges". No charges were ever brought.
The new information came as the coroner yesterday recorded an open verdict at the inquest in to Katy French's death.
The shocking revelations are contained in Mrs French's statement to gardai, which was made in the wake of her daughter's death in December 2007. She also claimed that there had been other incidents of violence against Katy. However, no one was ever charged in relation to these either.
A series of statements made to gardai following the death of the model reveal the seedy underworld at the heart of Celtic Tiger Ireland, where cocaine use was seemingly widespread.
They also show how Katy was in the grips of a cocaine addiction as she struggled with a turbulent personal life – details of which were played out in the full glare of the national media.
Katy's former fiance, restaurateur Marcus Sweeney, told gardai that when they started dating in 2005 she already had a cocaine problem and that it was around this time that he too started taking the drug.
Mr Sweeney told how he began sourcing cocaine for Katy and that the model was using it throughout the week and was a "two day on, one day off" user, whereas he used it as a "social drug" at weekends.
"Katy had no limit when it came to coke, she never wanted to stop, always wanted more," he said, adding that she suffered from palpitations and panic attacks as a result of drug use.
He recalled a night around Christmas 2006 in a room at the Westbury Hotel in Dublin when Katy was "coked out" and she attacked him.
As the model's drug habit worsened, he stopped buying it for her and by the time their relationship ended in February 2007, he had "slowed up" on using cocaine and was concentrating on his business.
He told how their relationship ended when he walked into his restaurant and found Katy lying on a table in the middle of a lingerie shoot.
"After having promised me she wouldn't do this anymore, I had enough. She broke my heart. I was in love with her, but she was intermingling with other men and I had enough."
He described his former fiancee as "hard work" and said that after their break-up, they got back together several times.
However, he ended the relationship for good around two weeks before her 24th birthday party at Krystle nightclub on November 29, 2007.
"I still loved her and would have got back permanently. Katy was seeing Jimmy Mansfield and she was playing me off Jimmy," he added.
Mr Sweeney said he believed "everything came on top" of Katy – the ending of their relationship and her disappointment at her birthday party, which she thought was a disaster – and that on the night she died Katy snorted cocaine "to a point of suicide".
In his statement to gardai, businessman Mr Mansfield said he was in an "off and on" relationship with Katy following her break-up with Mr Sweeney.
However, he did not want to be seen in public with the model, fearing the publicity. Katy wanted a commitment from him, but he was reluctant.
"I never went out publicly with Katy because of the papers and the likelihood that they would begin to associate us together and I didn't want that publicity," he said.
Mrs French told gardai it was around two years before her daughter's death that Katy broke down crying and confided in her that she had been using cocaine and that it was ruining her life.
Katy went to see an addiction counsellor and her mother believed she was drug-free. She believed Katy suffered a relapse because she was feeling down.
"I know...she was down about the press coverage of her (24th birthday) party."
Recording an open verdict at the inquest into her death yesterday, Coroner for Co Meath, John Lacy, issued a stark warning over cocaine use, describing it as a "very dangerous drug".
State Pathologist Marie Cassidy told the inquest Ms French had a "sip" of alcohol in her bloodstream and that a small amount of cocaine was also present.
He said someone who had given up cocaine but then relapsed and used a small amount could suffer "very tragic consequences".