The troop only realized the bills were counterfeit after the woman made off with $50 worth of cookies and $150 of their money, investigators said.
The scammer initially gave the girls one fake $100 bill for eight boxes, and got $60 in cash. On her way out from buying groceries in the store she got two more boxes with a second fake bill, and received $90 in cash as change.
Police describe Sunday's suspect as a white woman in her mid-30s with long, dirty-blond hair standing about 5 feet, 5 inches, tall and weighing around 150 pounds. She was accompanied by a small dog on a leash, and the scouts believed she was missing several teeth, officials said.