Foreshadowing

I'm rereading Sense and Sensibility, and I think Jane Austen nicely illustrates a certain lesson about deus ex machina vs. foreshadowing in this book. (Therefore, today's post contains spoilers, but I think that's permitted for a 200-year-old book. It's not like I'm revealing the ending of Mockingjay here.)

In S&S, Elinor loves Edward Ferrars, but he is already secretly engaged to a young lady named Lucy--an engagement made, we are told, when both were too immature and impulsive to understand ...