In the story I’m thinking of, the girl turns to inserting chloroplasts under her skin in a secretive act, becoming greener. In the book, she seems to struggle emotionally. She eventually becomes a plant and in my memory it is a welcome result for her. The word 'metamorphoses' comes to mind. Like Ovid, but more recent.
I read it around the time I read Amélie Nothomb’s The Character of Rain and wonder if they haven't spliced somewhat in my mind, but am certain that is not the book. The book I read took place in a space colony where the girl's father was busy. Asimov vibes here.
I don't think it was Catalyst by Lydia Kang.
And I don’t think it was The Cure for Love and Other Tales of the Biotech Revolution by Brian M. Stableford.
… the search continues so if any book or text comes to mind I would appreciate you sharing :)