This is such a well-told story that I am awed at Wharton's skill. It exactly depicts that feeling of a teenager breaking out from their home life and beginning to experience the world on their own terms without the mediation of parents or teachers. Charity's wonderful summer of discovery has moments of real magic, as she explores a world that seems shiny and new and fresh to her inexperienced eyes and she also finds a boy to share it with. But experience can be bitter as well as magical and she also finds out some things that change her view of herself and the world. The reality of life for girls in the latter 19th century was less than idyllic and Charity in the end discovers what she has to do to compromise and survive (unlike some of Wharton's heroines, who never figure this out).
If you have ever had a marvellous summer of discovery, or the memories of a gap year, or first year at university, you will surely recognise the emotion that Charity experiences, breaking out of her small world to discover something beyond what she had known before.