Trying and failing to search for the name of novel about a girl living on her own/hiding out in the countryside after a war. It was kind of a survivalist book, but way before that genre was a thing.

It was a book we had to read in school (aged maybe 9) back in the 80s in the UK. One of the first school books I loved! Would probably be classed as YA now. I'm writing a YA survivalist novel myself now and thought it would make a good comp to share with agents... thanks for any help!