Book where two high school friends get married and go to the Northern Lights

I'm actually looking for this book on behalf of someone else. It's a book where a high school girl likes her best friend's older brother. The boy puts post-it notes with quotes everywhere and he becomes a blogger/travel writer when he grows up. When they grow up, the girl encourages the boy to go see the Northern Lights and they do and get married (they might get married first). It had similar vibes to Anne of Green Gables and I'm pretty sure it was written by a female author. It was a contemporary novel in the 2010s or 2020s.

Any insights would be great!