Alternate Character Interpretation: While definitely sympathetic it's possible to read Tiffany as rather manipulative. It's revealed that she used information from Pat's mother to arrange "coincidental" meetups with him on his runs, she persuades Pat to spend time with her by promising to assist him reconcile with his wife, forges a letter from her and lies to him about Nicky will be present at the dance. She also displays conveniently encyclopedic knowledge of Eagles when interacting with Pat's father despite claiming not to like football earlier in the film.
Fridge Brilliance: Pat's Trigger for his stalking of the ex is "My Cherie Amour", a song about a guy who loves a woman from afar. Given that he's got a restraining order against him forbidding him from even being near the school she worked at as a teacher and she won't give him the time of day, she's as unreachable and distant to him as the woman in the song was to the singer.