Annapolis police have charged a 12-year-old girl with assault in the stabbing of a 13-year-old boy. The incident occurred at 11 p.m. Thursday outside a home in the unit block of Pleasant Street, near Clay Street. The victim was cut on the arm with a kitchen knife and was taken to Anne Arundel Medical Center, where he received three stitches. The suspect was released into the custody of her guardian. The juveniles are not related, police said.