Does anyone know this book?

[Saucery]

I read it in ‘81/82 as a preteen. It was about two girls of about 12, best friends, who made a pact not to grow up. Over one summer they embarked on an anorexia pact and one of them died. The other recovers iirc and she was always led by her friend rather than truly wanting to go through with it. Part of her regrets not following her friend though.
I don’t think I entirely understood what was going on and the idea of not wanting to get older wasn’t something I’d ever considered.
It was a British or European book, rather than an American one, so not Judy Blume or Barbara Wersba (which I also read).
I’m sure Summer was in the title but googling likely combinations hasn’t brought anything up.
I’d like to read it again to see if it was as mawkish as it sounds. I remember it as very thought-provoking and troubling, with maybe a folk horror/magic aspect to it?

Wintergirls? www.amazon.co.uk/Wintergirls-Laurie-Halse-Anderson/dp/1407171062/ref=sr_1_1?s=gateway&crid=27KO2RP7JAFUL&keywords=winter+girls+book&sprefix=wintergirls%2Caps%2C156&tag=mumsnetforu03-21&qid=1563261874&sr=8-1

Thank you sueelleker but it’s too recent. This book would have been published in 1981- 1983 or before. I read it in one house we moved from when I was 12 so I can date it to then.

It wasn't about cousins was it? In America

It feels like a British book to me, but I could be wrong. The anorexia was very much in the background iyswim? Sort of presented as a magic spell to halt the changes of growing up.

Second Star to the Right by Hautzig

The overall tone of it was very much like Harriet Said, by Beryl Bainbridge. I knew the main character was being led to do something very dangerous but hadn’t realised.

No, Byker, girl too old, unfortunately.

Maybe it doesn’t exist after all and I should write it!

It sounds vaguely like summer sisters by Judy Blume but not exactly

It does and I know I read her extensively a year or so later. Paperback editions of Deenie etc hit the small local library!
This was a hardback, yellow misty cover, long-haired girls in long grass?

It will probably jump out at me in a second hand bookshelf some day and I can put it with my copies of A Candle In Her Room, Dogsbody and If It Weren’t For Sebastian (the Tormented Teen Shelf).

I don’t suppose it’s The Summer Birds by Penelope Farmer? That has the element of two friends, one of whom decides in effect not to grow up . But I don’t think it has the anorexia element. It’s a strange Peter Pan type fantasy.

Thank you, pollyhemlock, I have read that one too, but it wasn’t that!