Sister should not be in her room only during late morning, early morning she's in room, late morning (or however it's phrased in game) she's at school, every other time of the day she should be in room.
You corrupt mother and sister in their respective rooms. Going on date/hanging out, or interacting in living room, kitchen, bathroom is just for extra scenes. Just do something else so that time passes, to get access to them in the room (like go to work, park, hospital, neighbor...) by the time you get back home they should be in their rooms, unless it's late night and they're sleeping.