Many might not want to hear this -- and I haven't read much about this project yet, so perhaps this is the direction already being offered, although probably not -- but I think the best way to adapt this is to keep the premise, but change just about everything else. I read the book a long while ago, and it certainly is a great story, but what I remember of it -- the abuse angle, the Space Cowboy, etc. -- probably won't work on screen. Instead, perhaps she should be discovered by a group of individuals on the run from the law after a short time period in which she is menaced by things from nature -- the dog, maybe a queen hornet building a nest, that sort of thing. Maybe she could be discovered by teenagers who wonder what they should do. In both cases, threatening to leave her there if she doesn't give them access to money would come up. Eventually, she could escape somehow and then hunt the group down in the woods, leaving one in her predicament. Maybe even the husband brings her there with the express purpose of trapping her. Who knows, but those are my thoughts at the moment.