This Can't be the real ending
Something doesn't add up. I have a feeling that the writer had a completely different ending and somewhere along the line, people wanted the "happy" ending.
First of all, the boyfriend is a shallow character of which we know very little. We have no idea if he really is a good match for her or not. Through the movie he ends up getting tired of her in the relationship and you begin to feel that they will end up breaking up and Amy will write a new book about it. Particular scenes are the bed scene where he's no longer interested and any scene after that until her final speech at Woman's March. It would have made more sense for them to break off, the guy used her or at least gave it a chance and the movie ends on a highlight of Amy writing another best seller. Happy ending! Yay.
Here's an entire scene that adds to my theory. The scene when the priest tells her that he was fired. That scene wasn't needed in the movie UNLESS they end up dating! I believe the movie was supposed to end with the two of them going out for a cup of coffee and really opening up. Follow up reasons: Amy's complaints about the lack of communication and confessions about past lives with boyfriend. This is easily done with priest. 2nd, the writer made a big deal about stating the Amy is looking for a jewish guy. Was the boyfriend jewish? Didn't come up. But we do know that the priest was catholic.
So there you have it. Flat boyfriend character and sudden super love ending just doesn't feel write with the tone of the end middle of the movie.