According to Tracy Spiridakos, Hailey not crying for most of that powerful final scene was a deliberate choice for her character, and the tears finally flowing arguably made the scene all the stronger as Hailey finally opened up to Jay.
In explaining that “I love you” reminds her of her dad’s way of apologizing, she cleared the air and shared her feelings in a way that doesn’t usually happen for any character on Chicago P.D. For his part, Jay really demonstrated how much he has grown over the years of knowing her in showing no hesitation about wanting to be with her despite all the baggage.