Debbie R. Miller, 41, of Appleton, also faces misdemeanor counts of disorderly conduct and resisting an officer.
Miller claimed to find the rat in her lunch April 17 as she ate at the upscale Seasons Restaurant in Grand Chute, according to the criminal complaint.
She threatened to alert the media unless the owners paid her $500,000, the complaint said.
The owners turned the rat over to their insurance company. Investigators there determined the rodent was a white laboratory rat, the complaint said.
Tests also suggested the rodent had been cooked in a microwave, but the restaurant doesn't use microwaves in cooking.
Miller said the incident caused her to seek unspecified medical treatment. She was being held Monday in the Outagamie County jail in lieu of $1,500 cash bond.
Court Commissioner Brian Figy said the bond amount reflected Miller's lack of a criminal record.
"The defendant may have some physical or mental issues and has no warrant history," Figy said. "But the allegations are rather disturbing."
Online court records did not list a defense attorney for Miller, who is due back in court Thursday for further proceedings. The extortion charge carries a maximum penalty of 3 1/2 years in prison.
