Humm, you must be very careful with this, as women are fucking crazy. If you plan out HER day off she might get pissy because "I work 7 days a week and the one day I get off you have us running all over town". Now your intentions are only the best, but you might want to ask her what she would like to do. Let her know that she works hard and that you appreciate that and you would like to treat her to a nice night out to thank her for all she does. Then ask her if she has a preference. That way if she feels like staying in and watching old movies in her sweat pants she has that option. But if she want to go out and “party” then get a reservation somewhere and hit a bar after, maybe invite some of your couple friends. Bottom line is that you want to make her happy, so if I were you I’d ask what she wants then plan accordingly… Good luck!