From technical point of view, the movie is probably 6 stars movie. However, the movie does small and little things right and it does the basic stuff right. After the final act, it almost feels like I want to give it 8 because the movie concludes everything what is required considering what the movie gives at the first act. Story gets captivating to follow that what is going to happen next. It's actually brilliant in that sense.
The movie is cruel in places but I suppose that it is the purpose of the movie and thus it delivers what it's expected. What comes to violence or gore, I think that it's managed very well. Not too little or not too much but good balance in right places.
Laura Galan (Sara) makes actually superb performance. She plays her part very well and I think she manages to kind of trick the viewer by the end of the movie. Too bad that the villain is not that convincing since it's almost like a the beauty and the beast kind of story. I also did like Carmen Machi (Sara's mother). She plays her part very well. I think she actually turns some things in the movie to comedy but at the same time she's very convincing.
The movie would be totally 8 starts or even 9 with a little bit of bigger budget and little bit of refinement in the overall production. Go and see it.