Book about girl who's sister dies, girl then likes dead sisters boyfriend /s

[Bronagh]

Cover is blue and I think had clouds on it, had a piece of elastic that went around it
Girls older sister has died think it was like a random death, girl likes sisters boyfriend and I think they do stuff but eventually agree it's wrong, but has another guy who she eventually gets with, he's like a friend figure throughout most of the book
Think she lives with grandparents or aunt or something?
Girl also writes notes/poems and will just drop them in the street leave them in random places etc
Think the girl also felt in the shadow of her sister that died

[Christie]

I'm going to have to go through my list of books read because I'm almost certain I've read this one.

[Diana]

This is The Sky is Everywhere by Jandy Nelson.

[Christie]

That's the one I was thinking of. :)