Saturday Night by Marjorie Holmes (1959)
Danny is the most popular boy in town, a Peter Pan who won't grow up, with faunlike ears and merry, carefree chatter. He takes her to the Copper Kettle, where the high school crowd hangs out, for grilled cheese and a Coke. Carly knows that the really popular girls have in turn all been his steady dates, but he sweeps her off her feet and she now becomes "his girl." As such, she finds that she has become popular ... she belongs. She feels, however, a strange misgiving in the welcome she receives from the others, and her forebodings prove to be all too well founded.
Much of the action of the story centers about the lake, beautiful, fascinating, but able to assume a dark and tragic aspect too, as Carly learns to her horror.
The reader who follows this typically American girl through the experiences of her first love will learn, as she learns, the truth of what her father says to her: "Hurt is simply a part of growing up. It's as inescapable as -- as cutting teeth." (from the inside flap)