Do I treat my daughter like a slave?

NO! Not at all. If you are paying her good money she should be more the willing to do a couple of chores.If I were you I would start to make your son to do a chore or two. That isn't fair that does all of the chores. If she goes to parties or likes to hang out with her friends tell her " Do your chores or when you should be hanging out with friends you WILL be doing your chores" I really hope this helps.