The mother of British-Lebanese schoolboy Yousef Makki, who was stabbed to death last year, has died of a "broken heart", her family have said. Debbie Makki, 55, died on Sunday almost 14 months after the death of her son Yousef, 17, who was killed after a fight with his friend Joshua Molnar, 18, in the upmarket Hale Barns area of Greater Manchester on March 2, 2019. Following a trial last year, Molnar was acquitted of murder and manslaughter but was initially jailed for 16 months for possessing a knife and perverting the course of justice. He was released in February. Mrs Makki had been campaigning for a retrial prior to her death. Her daughter Jade Akoum has vowed to continue to seek "justice". "She hadn’t been the same since Yousef was murdered," she said. "Her heart was broken and the spark in her eyes had gone. " Ms Akoum said the toll of losing Yousef was "colossal" and said her mother's continued fight for justice meant she "never found peace". "At 4am my beautiful strong mum Debbie Makki peacefully passed away," she posted on Twitter. "God rest your soul, at least you are with Yousef now, we told him we needed you here a bit longer but you had to be together! We love you so so much, i promise we will keep fighting for justice." “It is with a broken heart that we have to share this devastating news: our beloved Mum and Nana, so loved by everyone who knew her, died in the early hours of this morning," the family said in a statement. “She was rushed to hospital via ambulance two days ago after struggling at home. The doctors told us she was critical. She was not strong enough to fight. Lockdown isolated my mum from her grandchildren who kept her going and she had too much time to think about the loss of Yousef – and the stark injustice and inhumane treatment of our family that followed. “She wondered why the the families of the boys involved in Yousef’s death have never contacted her and how they could be so cruel. It kept her awake most nights – she literally never slept. We were unable to be with her in her last moments, just as we were unable to be with Yousef – but they are together now which brings us some comfort. Our world has fallen apart all over again and we are all in complete shock.” Mr Makki's family have criticised the investigation into his death, which was carried out by Cheshire Police and Greater Manchester Police. At present, both forces are being investigated by the Independent Office for Police Conduct in relation to the case. Under UK law a person can only be retried if new evidence comes to light. Mr Makki was a bright student studying at the prestigious Manchester Grammar School when he died on March 2 last year. He suffered a stab wound to the heart.