Ten years of birch, one day of chaga.
It probably describes the relationship between them.
She loved him for nearly ten years, but he left her resolutely. She was originally shaken by his return, but in the end, he turned into a boss and tortured her.
In the beginning, she was the birch tree, and she thought he was the sunshine.
In the end, she understood that she was the birch tree, and he was the chaga that had absorbed her essence for ten years and forced her to die.
They are both right, it is all the fault of time and the initial lack of love.