Is the movie what if fiction or based on a true story?

"What If" is a 2013 American romantic comedy film directed by Michael Dowse and written by Elan Mastai. It is loosely based on the short story "Sliding Doors" by Emily Giffin. The film follows the lives of two versions of the same woman, one who decides to chase after a train and one who decides not to.

So, the movie "What If" is a work of fiction that was inspired by a short story. It is not based on a true story.