This is the latest film interpretation of the Frances Hodgson Burnett children's book of the same name - I've seen none of the previous versions. This one stars Dixie Egerickx as Mary Lennox, a young girl whose parents both died in India (1947, the fighting during Partition). She's sent home to England to live with her depressed and reclusive uncle (Colin Firth, but his role in the movie is very small), and pretty much left to her own devices in an immense house on a very large property. Mary Lennox gets some leeway having just lost her parents, but is by any measure an obnoxious child. Although the friend who watched it with me tells me that Mary is far worse in the book (and that it was originally set around 1900).
The original book isn't fantasy (although it does sound like it has prophetic dreams), but this movie is: it could have been called "The Magic Garden" as plants move to assist climbing, or bloom or wilt in response to events. The fantasy elements of the film were unnecessary, it could have been just a (beautiful) garden and the outcome of the story would have been the same. I think it has been in previous interpretations. They added nothing to the story by making the garden magical - in fact, they distracted from the people as we watched for what weird things the garden would do next. Firth's role is minor and adds nothing to the story, and the resulting movie is kind of "meh."