There are several versions of the lyrics for this song. The version Grace sings is the "Sufjan Stevens" version, which is very close to the official version. The "James Blake"-version and the "extended" version have verses that are much more "adult" in content. We of course don't know if Grace is singing the "innocent" version on purpose or because it is the one show knows about. However, her style of singing it also differs significantly from the original which, while not "adult" in content, is definitely sexually suggestive in the way it is sung.