A 46-year-old Bergen County woman was arrested Monday and charged with assaulting a child who was in her care, authorities said. Stacey A. Wilmarth, of Dumont, was charged with aggravated assault and endangering the welfare of a child, both second-degree crimes, over an alleged crime that was first reported to police on May 27, according to Bergen County Prosecutor Mark Musella. “An investigation by the Bergen County Prosecutor’s Office and the Dumont Police Department revealed that Stacey Wilmarth physically assaulted a child under the age of 13 years old who was in her care,” Musella said in…