Symbolism of Tracey Fragments decoded

Spoilers ahead!

This beautiful metaphor-laden movie is in its essence really only about a girl becoming woman. Or, a teenager, rapidly being hurled into adulthood catalyzed by chaotic events in an inhuman environment.

Bear with me, this will make sense toward the end:

Her brother Sonny is a child, representing childhood, in fact **her** childhood, that she must learn to leave behind. Sonny serves as a symbol of the playful innocence that we all struggle to let go of when we progress towards adulthood. My interpretation of Sonny being merely symbolic is underlined by the omission of any communication from him other than his barking (barking = animal-like, roaming freely, innocent). I believe this way Sonny's character was intendedly kept to a minimum by the author so that viewers wouldn't more easily ascribe any character to him, as this would have made him a "real" protagonist with a story and thus distracted from the symbolism. Her literal saying "I hypnotized him" can on the symbolic level be understood as her saying "I put the child in me into zombie mode (and pretend to have grown up as most teenagers do), but(!) it still barks for attention".

The telephone call where her mother hangs up the phone (cord), not answering is highly symbolic of the (umbilical) cord being cut, of her being thrown into a (to a child) seemingly mad world of adults, with no help to be expected from even your parents (who themselves, as messed up as they are portrayed, in their own way never really came to terms with fully growing up)

All throughout the movie we hear people warning of a blizzard coming, a mantra metaphorically outlining her as still being a child who needs to be patronized and cannot lookout for herself yet. To be understood in the sense of "stay inside children, the (adult) world out there is a dangerous one". When the blizzard finally comes at the end, with a calm resolute expression on her face she walks freely through it, capable of dealing with a blizzard (adult world), marking her arrival in adulthood.

The question whether or not her brother Sonny really died is ultimately irrelevant to the meaning of the movie since what counts is that the symbol that he stands for most certainly *does* die when she looses her virginity (her childhood, her innocence) in the car, which is also the *exact* moment that her brother goes lost plot-wise(!), - a timing very wisely chosen for the symbolic narrative.

So, her childhood is lost at this time but adulthood not yet found! Hence, existential chaos and rage ensues as she is suspended in between the two and struggles with the process. Superficially on the plot level, we (and her, as she realizes it only then fully) only learn at the end that he probably died in the water, and it isn't until this realization of hers (that her childhood is not only lost but has died) that her facial expression changes to one of acceptance, one of being capable of facing whatever may come, now ignoring Billy Zero, walking past him and off into the blizzard (adulthood).
She unwillingly undergoes this progression to adulthood in a very fast-forward manner, as she --all within the space of days--
- looses her virginity to an insensitive prick,
- realizes her mother does not want her home anymore,
- slashes someones throat after getting almost raped and killed,
- throws herself into the madness of the city, sleeping in busses etc,
basically descending into a form of purgatory before coming to terms with her new found reality and self.