The Daily Herald of Everett reports that Michelle Davidson is due to appear in Snohomish County Superior Court on Monday. She is being held on $250,000 bail.
Investigators said she shot 52-year-old Dean Urness in the chest at about 1:30 a.m. on March 31; a copper BB was found embedded in his right lung.
Detectives say the shooting occurred on a property with more than a dozen vehicles, including motor homes and travel trailers. Davidson and her boyfriend considered themselves caretakers, and they asked Urness and his girlfriend to leave.
Davidson's boyfriend and Urness had been arguing when Urness was shot. The boyfriend told police that he didn't think Davidson needed to protect him.
Prosecutors filed the murder charge Friday. They allege Davidson intended to assault Urness and as a result caused his death.
State Health Department spokesman Donn Moyer says his agency's data show only one reported death from a pellet gun in Washington between 2007 and 2011.