Fiction by Harriet Lane.
At the beginning of this book, the main character Frances witnesses a car accident. At that moment a whole new set of events is suddenly in motion, or perhaps it's more accurate to say that Frances suddenly has a choice to set this new chain of events in motion.
This story is a psychological thriller, but a quietly British one, not a fast-paced type. It was very interesting to read.
Note: I liked the cover on the novel I read better.
(Alternate cover art is from http://www.beniceorleavethanks.com. Go there for a better review than mine!!)