The book was older and faded back in the early 90s, the art reminded me of the style of Stephen Kings Dark tower. It was found at a school library in the older kids/adult section and was defending fiction. The cover had a young girl with a solemn look in a red medieval dress sitting at a castle window. I remember something about a war or battle and it may have even been what she was watching out the window. I also remember a tilted drafting type table or needlework stand beside the girl. I was 9 when I started to read it and was told it was “too old” for me so it was taken before I could read more than the first couple of chapters.
Long shot, but maybe ‘The Nine Days Queen’ by Karleen Bradford. Some of the covers are a partial match, and I can see the premise being considered a bit much for kids. (Ann Rinaldi’s ‘Nine Days a Queen’ is another possibility, based on the same historical events.)