Just watched it today on Netflix. I enjoyed it but it kept bugging me that I've seen this (story) somewhere before. Then it hit me, The Simpsons totally ripped this movie off in an episode. Not really surprised it wasn't mentioned here since it was a Lisa episode.
shareLisa the Drama Queen https://www.imdb.com/title/tt1291173/
Lisa and her new best friend create their own fantasy world, but Marge doesn't want Lisa to see her friend anymore after she finds out that they're too far gone in it.
The story of Lisa and Juliet is a reference both to the Parker-Hulme murder in 1954, New Zealand, and also to Peter Jackson's Heavenly Creatures (1994), a film based on the same murder.