The premise is one of how you interpret the visualization. To state too much of what it is about starts off the film and would be spoilers, so let's leave it at a young teen girl that stumbles upon a very traumatic situation that she isn't fully capable of understanding and how she compartmentalizes this event. The director uses surreal art quality scenes to show there was earlier trauma within the family dynamic that brought along her ability to deal with things by letting her mind go to an "otherwordly" head space. These scenes of where she takes her mind might not be for every viewer ability to grasp but that's what makes this unique. Reminiscent of another film from a couple of years ago, "I Kill Giants" which I also enjoyed because it showed another angle, grief from losing a mother ro cancer and how it was also dealt with internally, through the eyes and mind of a young girl.
That's also where the similarities end, as this not only deals with much heavier adult themes, it touches on how vulnerable a developing mind is, and how trauma can damage it, yes, even when A child loses a patent by divorce. Instead of the usual tropes to unpack these weighty psychological issues, this film goes for not so subtle visuals to show the trauma within and literally how she "slays" that metaphorical dragon that holds her back during the most challenging part of her ordeal.
Great acting. Solid script. Amazing visual content. Very memorable film, though yes, there is rough scene, that's some have alluded to and if you feel uncomfortable during this opening scene, than it did the film and writer justice ad it was handled in its rarest and brutal form without exploitation, but showing you why this sequence was as damaging as it should be for a child to witness.