The premise and plot are good. Actors did a good job too. My main objections are three:
1. I didn't like the handheld shaky cam cinematography. I thought it was inappropriate for the story and made it difficult to get perspective on the settings.
2. They don't really explain much about Chiara as a person. All of the energy is given to how she reacts to certain situations, but there's not much explanation for why she, unlike her sister, reacts as she does. We are expected to take a lot for granted.
3. They could have cut 30 minutes from this movie without losing anything. The first half in particular takes forever to get where it's going.
All in all, it's worth a watch. I am surprised it won a major award at Cannes. It seems very film student-y to me. Lots of good ideas weighed down by not knowing when to stop with the cinematic flourishes and just get to the storytelling.