I've seen this happening in both movies and in real life:
The relationship is over because either he cheated or was a jerk and all of the sudden, he shows up with flowers or gifts, hoping to win her back. Isn't that already insincere? Gifts are suppose to be during your happy moments (at any random date, not necessarily on her b-day nor Valentine's Day, any day), because it's a gesture of love... not because you're trying to win the girl back.