I remember reading a YA novel in the late 1990s in which a female protagonist makes friends with a family of talented musicians and academic geniuses who in fact turn out to be aliens. I remember very little of the story except that it has a sad ending.
I remember that the family were all named after tube stops on the London Underground and the protagonist makes friends with the eldest girl who is called Archway or Archie. Archie is depicted as being effortlessly graceful and mysterious.
I believe that there was a romantic implication between the protagonist and the elder son of the family.
The protagonist is unhappy with her home life.
I seem to remember that there is an old ruined church or similar that plays an important role within the story particularly with the father of the alien family.