Hopefully you can help me find this book. I’ve been searching for it for the better part of 10 years. The book would have had to be written no later than 1999.
I only have vague memories of the book. What I do remember of the plot is this:

Angsty teenaged boy is really smart. His parents are rich alcoholics that don’t really care about him. One day he decides to pack up, leave home, and live in the wilderness. He survives living in the woods for a little while, but does eventually start to have some trouble. He later meets a woman that also lives in the forest and has been for years(?). They quickly become friends, and the boy starts to become attracted to the women. They live together happily for a few weeks/months until winter starts to set in. One day they’re out hunting/foraging when she.. dies.. somehow. I think she slips and falls down a waterfall or creek and breaks her neck/back. The boy, distraught and panicked, buries or cremates her.
Now depressed the boy sets out further into the wilderness in full-on winter. He gets frostbite and I believe he finds shelter at some point. He sets out once again and at some point he passes out in the snow and later wakes up in a hospital with several of his fingers having been amputated.
The story may have been told in the past tense, while the boy spoke to a counsellor in the hospital.