I read a book in yr 9 that I’d love to find again as one of the main characters has is eerily similar to my mum.
It was set in Australia, (I’m pretty sure it was in brisbane).
It was about a young boy who met a older girl. The older girl had a tattoo on her shoulder/back of a horse or pegasus.
The girl was addicted to drugs, I’m 90% sure it was heroin.
Near (or the) end of the book, the girl went to rehab and the boy visited her. He took the train and she was pregnant.
On the version I had, it was of the girl, showing her tattoo and looking towards the viewer.
Sorry for being so vague!