Jackson was among 300 demonstrators outside the jail on Wednesday, where they broke through a police barricade to storm the prison where 41-year-old Wanda Jean Allen has spent 12 years on death row.
Allen's execution by lethal injection was slated for 0300 GMT in the Oklahoma State Penitentiary in McAlester, 190 kilometres distant from the jail where she was held.
Allen, who had a history of criminal violence, was convicted in 1988 for murdering her lesbian friend. Jackson has appealed to Oklahoma Governor Frank Keating to lift the death sentence in Oklahoma.
The first of seven executions slated for January took place on Tuesday.
Jackson charged that Oklahoma is a "kiling machine" during Wednesday protests. Allen is the first woman to be executed since Oklahoma gained statehood in 1907.
(dpa)