I found this movie to be quite dark, but also relatable, not in terms of the Highlands, of which I know very little, but being left behind after suicide. I did not realize, until looking it up, that Gillan directed. I only looked it up because I wondered if that was her Ronan the Accuser co-star, Lee Pace.
All that confession out of the way, I will say that I wasn't entirely sure, at first, of the flashbacks, whether they were or not, but that was my only complaint, really. I did not think, as some did, that the movie was a comedy, so that allowed me to avoid that disappointment.
The movie is very quiet and still, but given the subject matter that seems an appropriate choice. The long shots of Gillan's perfect face, though often zoomed in so we saw only her face and not her whole head were good choice, because it focused us on that alternating sense of emotional death and pain that she conveys wordlessly through expression. Once I solved the flashback problem (or believed I had, and turned out to be correct), I recognized the choice Gillan was making. Those memories and ghostly appearances by her deceased friend are difficult to capture in film, but the intrusion of memories in the form of flashbacks, though confusing at first to me, definitely convey how memory can work after a trauma. One is simply going about one's day, and then "bam" one sees a bridge, or person or whatever and all the memories flood back. It was very sad.
Gillan's character was tragic, and the 'about this movie' does not full capture what the true issues are.
I would summarize this movie as "The story of a young Scottish woman, awash in seeming decadence, while trying to cope with the haunting reminders of her friend, lost to suicide." I think if people saw that description before sitting down to watch they would be less surprised, and would know to look behind the initial drunken shenanigans of the protagonist.