So I'm writing a sort of post-apocalyptic story about what the world is like when the oil runs out, assuming that it does. My story has three threads: a history book current with my universe, which takes place a generation or two after there is no oil, the MC who lives in that time, and her ancestor's diary, written only a few years from our future. I have a really clear timeline of how things went down, a clear idea of what the universe is like: sort of like the Village, but everywhere, lots of eighteenth century influence. The ancestor I know what I want to write about. But I can't figure out what my main character, Sarah, wants to be doing, or what the conflict is going to be. I've put in a potential love interest, but I don't really want it to be a romance novel as such.

I know this is a really general question, but I could use some ideas for a conflict.