Mr Justice Griffith Williams, who presided over the trial at Mold Crown Court, told the court he wanted "time to reflect" before passing sentence, though he warned Smith her life sentence was fixed by law.
During the three-week trial, the jury heard that Smith had a "propensity" to threaten people by saying she would burn their houses down "with their children inside" and made a string of threats to Ms Shiers in the weeks before the fire.
They were told Smith had been increasingly angry with Ms Shiers, accusing her of being a noisy and untidy neighbour, and that she complained to others about Ms Shiers leaving the pushchair in the hallway.
Today Melanie Smith will be told the minimum term of her life sentence.
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The Lesbian, Gay, Bisexual and Transgendered communities in Cardiff are celebrating 30 years of campaigning; as part of LGBT History Month.
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