Dear Annie: How do I stop being my messy little sister’s personal maid?

Dear Annie: My 14-year-old sister leaves her papers and schoolwork everywhere -- in the kitchen, the living room, even the hallway. Every time I ask her to please move it into her room, which is an utter disgrace, too, she replies that she will do it later. And yet, days later, it’s still in the same place. This results in me bringing it all up to her room for her, only for it to end up right back where it was.