It’s been awhile since I’ve seen Fireproof. But was the wife a Christian when she did all those wrong things? I seem to recall the husband became a Christian first, and that’s why he repented. Also, the point was that the wife did not “deserve” the husband’s love and sacrifice at that point, but he had to give it anyway...just like we don’t deserve Christ’s love and sacrifice, but He gives it, anyway. That was the whole point. And I think the happy ending was that the wife also ended up coming to Christ. Therefore, she would have repented, though they may not have shown that on screen.
It was the husband's repentance and coming to Christ that helped lead his wife to Christ as well.
It's just that the focus was on the man's journey, and not the woman's.