SOLVED. Children's lit dystopian read in 2012/11- girl discovers community in which people have been brainwashed. The community has walls no one can see over the top of and everyone is controlled

[Eva]

I read this as a child and have been looking for YEARS. It was a great book. I can't remember loads there was a female lead she discovered a community where everyone was being controlled or brainwashed. The community had high walls that you couldn't see over. I think she was there because her parents died? - That isn't a spoiler because her being there took place very early on.
SPOILERS AHEAD
She finds a boy in this community and they somehow escape and then they manage to get to the female leads' grandparents house- that's like in a remote mountain place. That is the bit that I remember most but obviously that is a huge spoiler. I WOULD BE SO GRATEFUL FOR HELP.

[Eva]

Insanely my old English teacher still works at the school and told me its the silver crown. This is a horrific description of that book I apologise for greatly

[Kris]

The Silver Crown by Robert C. O'Brien