Tween/Kids book about girl who’s twin sister died on their birthday

The death happened before the events of the book (I think it’s been a year since) and it happened at a birthday party for the two girls. It’s set in England I believe.

She either had an allergic reaction to something or she choked. I think either way it was a peanut.

I believe the book focuses more on the aftermath of her death within the family and is narrated by the surviving twin. I can’t remember her age but I think between 10-12. I do remember there was also an aunty who was an alcoholic.

I read it in 2017-2018 in school so it’s not a thriller type.