Williams, of Ruperra Street, Newport, admitted killing Dowsell outside a property in St Vincent Road near the city centre in the early hours of 18 July. Gwent Police armed officers were called at 1.37am after reports that Dowsell was bleeding. She was found a short distance away near Chepstow Road.
Despite attempts to save her, Dowsell was pronounced dead at 3.15am. A post-mortem examination found that she died from a stab wound to her left back, which injured her lung, stomach and liver.
At the hearing, Judge Tracey Lloyd-Clarke told Williams that since he has pleaded guilty to murder, the only sentence the court can pass is life imprisonment. Dowsell's family, who were in the public gallery, broke down in tears as the plea was entered.
In a statement, the family described Dowsell as the "foundation" of the family and said it was "heart-breaking" that her four children had been left without a mother. "You have left us broken-hearted – we are all in shock. We don't know what to do but we are finding comfort in the memories we have of you," they said. "Four children without a mum is just heart-breaking."