The terrorist group claimed she died when a Jordanian aircraft struck the building in which she was located in Raqqa, Syria.
The militants said that none of their fighters had been killed in the air raids.
Jordanian fighter jets bombed Islamic State sites on Thursday, after the militants burned to death a captured Jordanian pilot.
The State Department told Sky News earlier this week it was working "very hard" to free the aid worker.
President Barack Obama recently said officials were in close contact with the woman's family.