SOLVED. Childrens/ YA Fantasy about a twin girl who is lying about her twin's powers. Spoilers ahead. [s]

[Lance]

I read this book anywhere from 2010-2014. It was about a twin sister who's twin couldn't speak properly but there was a class of people that could basically astral project and the girl was lying to the test givers about being able to both understand her sister and that her sister had these powers. I think it was set on an island?

SPOILERS AHEAD
Her sister does actually have these powers and it turns out she was astral projecting to a different village and learned their language. There was also some sort of plot to kill all these people with the powers or take away their power or something and the book is mostly about the twin without the powers running away from being killed with her sister and a friend I think, might be a bit wrong on those details

[Becca]

Sounds like Gullstruck Island, also published as The Lost Conspiracy, by Frances Hardinge.

[Lance]

That is it thank you so much!!!