Needing advice! abo my sister in law

So my 13 year old sis in law occasionally babysits my younger children while I need to run errands etc, an several times I've come back unexpectedly within min of leaving, an caught her rummaging around in places that she's not supposed to. First, she tried my wedding dress on that was in the closet, second, I caught her putting my makeup on in my bathroom, I'm just wondering, am I wrong to get irrated AN mad that she's in my personal space without permission? I don't want to ruin our relationship by telling her to stay out, but on the other hand I'm sick of finding makeup smeared on my countertop every time she babysits. Any advice? Or I'm the only one making a big deal out of nothing?