Western witch killed the film?

Last Sunday was my wife's birthday. At her request we went to see a movie titled "A western witch died". Japanese title 西の魔女が死んだ
The story develops around a truant high-school girl, Mai, who, following the suggestion from her mom, gets to live with her dearest grandmother instead of unwillingly going to school. Living in a house surrounded by forest and affluent nature with the elegant, "witch" grandma of British origin, Mai learns a lot about doing everyday things or making decisions on her own through the training to become a witch herself. One day, as the peaceful days go by and the training takes its course, she makes her own "decision" about a man living in the neighborhood that he is a bad guy, on which her grandma disagrees. The admonition from grandma about her obsessed view of the man ignites her hysteric, uncontrollable explosion of emotion that causes the grandma to slap her hard on the cheek in an apparent attempt to make her see what the words cannot convey. Of course she fails to understand the wordless word and feels estranged from the grandma. She decides to go back home to live with her parents. The scene of the grandma seeing off Mai was moving. She just stood at a gate with a calm but sad look as the car carries her dear grand daughter away. Two years have passed. She comes to grandma's house again to see her. This time grandma was lying on a bed with a white cloth covered on her face. She passed away as she implied to Mai two years ago. There is a cup on the table. It was Mai's. A flower is put in the cup, as if a trace of love to Mai from grandma. On the fogged window near the plant Mai had treasured, there left handwritten words, "From Western witch to Oriental witch. I successfully got out of my body."
Sachi Parker who played the role of the grandma was only good when she was silent. Once she speaks it annoyingly reminds us this is just a movie, only a fiction. It was regrettable all the more because the new young plain-looking actress playing the part of Mai was plausible and good.
The story was apparently meant to bring home to us that we have forgotten our soul and spirit. The theme may be good but only it was cheaply depicted. Hopefully it is better in the original novel since it was not killed by the Western witch.