A fast-food worker tossed a cup of hot grease on a customer, giving the woman second- and third-degree burns on her arms and chest, authorities said.

"My skin was cooking," said Vouncile Lambert, 44, who was treated at a hospital.

The 17-year-old worker was charged with aggravated assault. The employee, who had worked at the Checkers restaurant in West Philadelphia for about two months, will be fired, a restaurant manager said Wednesday.

Lambert's 36-year-old niece had spit on the employee, a police report said.

Shaji Joseph, an area manager for the hamburger chain, said the customers were upset when the employee closed the walk-up window on them Sunday afternoon.

"Nobody would just throw grease at somebody without provoking," Joseph said. "(But) we totally understand she can't throw grease on her."