It's Punky Brewster

At summer camp, an Olympics competition is staged between camps Towering Pines (where Margaux is staying) and Tumbleweeds (Punky's camp). Punky single-handedly wins two events but Margaux accuses her of using Glomer as an assist. Glomer offers to stay with Margaux to help Punky save face, but when ensuing events go wrong for Camp Tumbleweed, Punky suspects Glomer of being a traitor.