LONDON (AP) — A British woman has been sentenced to at least 30 years in prison for the January murder of a woman she considered her love rival.

Sarah Williams shot 60-year-old Sadie Hartley with a stun gun at Hartley's home in northwest England, then attacked her with a kitchen knife.

Prosecutors said 35-year-old Williams had previously had a fling with Hartley's partner, Ian Johnston. They said Williams continued to send Johnston explicit texts and photos, while plotting the "perfect murder" of Hartley.

Williams and accomplice Katrina Walsh were convicted Wednesday by a Preston Crown Court jury. Both had denied murder.

Judge Mark Turner sentenced Williams to life with no chance of parole for 30 years, and Walsh to at least 25 years, for "a crime of obsession, or arrogance and of barbarity."