It's not okay to lie to someone in a relationship.
George does not have to work this weekend.
George wants to go to the football game but knows that his girlfriend wants to go to the Oktoberfest.
George tells his girlfriend how much it means for him to go to the football game with his buddies.
George tells his girlfriend that he has to work and instead goes to the football game with his buddies.
George's girlfriend understands and agrees that they can do something together the next time George has off for the weekend.
George's girlfriend ends the relationship when she learns that George did not have to work and actually went to a game.