Well, I guess you can leave her in the room and go do your own thing that way! That is, as long as she doesn't call you in the middle of a sweet gambling session and say, "I'm bored...when are you coming back?" Grounds for immediate eviction, sister or not. Best to set down the rules from the start.
On sleep: Yeah, I figure if you come back from Las Vegas well rested and happy, then you really didn't do it right. If you come back dead tired, hungover, and deeply saddened by the fact that you had to leave, then you got your money's worth.