How to Deal With....

So this little shit (my niece) who I know is staying over for 2 weeks while she has her school holidays, and I really suspect she is going to snoop through and steal through my stuff while her parents are away. Now noone enters my room but myself, so if I close the door, what should I place in it to tell if someones entered? Just a bit of paper? It's well known shes a little shit, so I have no qualms about confronting her If I find that piece of paper or whatever disrupted.

Do 4channers have any tips or experiences with younger siblings etc? Killing her is out of the question sorry.

Yeah like I said before, you are the only one concerned with proof, Anonymous has all the proof it needs (from you still posting here)