The non-canon Green Hair Barefoot Sengoku Nadeko wearing a white Sundress that appears in the Nademonogatari anime opening Caramel Ribbon Cursetard (YouTube link As in the OP, she normally appears with several identical clones. Up to 11 appear on-screen at once.
Not to be confused with the much less childlike green-haired Nadeko in the Ren'Ai Circulation or Mousou Express openings.