For those interested in the real-life Kopp sisters - here's a link to BookBrowse's "beyond the book" article on the topic:
https://www.bookbrowse.com/mag/btb/index.cfm/book_number/3280/girl-waits-with-gun#btb
(for a limited time, all visitors can browse this article, which is normally only available to members).
And here's an interview with Amy Stewart about why after years of writing nonfiction she turned to fiction to relate the story of the Kopp Sisters:
https://www.bookbrowse.com/author_interviews/full/index.cfm/author_number/2703/amy-stewart