Sheila is a character featured within The Minish Cap. She resides in Hyrule Town and can be seen walking around the town throughout the game. She will give Link some clues about some secrets, including an old legend that something big will happen when Hyrule's bell rings. This is in reference to a Piece of Heart Link can get by flying into the bell using Roc's Cape. However, she presents this information to discourage the behavior, stating that everybody is afraid of what might happen.
Link is able to fuse Green Kinstones with Sheila at various points in the game. As it is a Green Kinstone fusion, it is not set to a specific treasure chest, but instead, one of the many possible treasure chests.