I watched a movie about this woman who was engaged to this really self centered man but then her old imaginary comes to life and they grow closer and even fall in love with each other

The movie you are talking about is:
Sundays at Tiffany's

Here is a link to information about the movie: Sundays at Tiffany's (TV Movie 2010) - IMDb (http://www.imdb.com/title/tt1743360/)

The movie is very good and I saw it on TV a few months ago.

There is a funny one from the early 90ies called Drop Dead Fred,with similar storyline. Check it out if it's not the one pready suggested

https://m.imdb.com/title/tt0101775/