From babysitting to part-time work in a business on weekends, there is plenty of work for her to seek out. If she counters your request that she find work with a complaint like " But all my friends' parents don't make them work!" you can say that your family believes in giving her the chance to take personal responsibility in this area. Tell her that she has not had to do it up to this point (perhaps you could admit that you should have insisted on it sooner) but now it's time.
"Get Out of My Life! But First Could You Drive Me and Cheryl to the Mall?" by A. Wolf is a thoughtful book on parenting teens.