Georgina Furtado Vilella killed her 45-year-old husband Carlos in a huge house fire at the couple's terraced home at Walsall in West Mids on March 28, 'Daily Mail' reported.
A murder jury at Wolverhampton Crown Court heard that everyone else was asleep in the house apart from 46-year-old Georgina at the time of the attack.
Three of her four stepdaughters aged 13, 17 and 21, who were also asleep in the house, managed to escape the blaze, but Carlos' 14-year-old daughter received "dreadful injuries."
Prosecutor Peter Greaves-Smith told the court that she had bought a petrol container and filled it with five litres of fuel before pouring the liquid on her adulterous husband as he slept.
Georgina, however, denies murder and arson with intent to endanger life. The trial, which is expected to last two weeks, continues.