I need advice...

I might sound a little ridiculous but i just need to vent... My stepdaughter is 15 and Recently I have caught her taking my bras and thongs. I was so upset, I spoke to her about that and of course she denied it but that's ok. I was mad when I found them but then thought to myself when I was 15, I wanted the same things. Anyway, she uses my stuff without asking. It's like she doenst care. I bought a hair spray that I swear I've probably only used about 3 times and it's almost gone bc she always uses it. I mean, I don't go to her room and grab her stuff so I find that rude. Today I found my hair spray in the bathroom and I have no idea how it got up here when I remember  taking it downstairs to my bedroom. If she was to know I use something of hers, she will say something and have a fit bc of it. I just don't like her using my stuff without permission. Am I over reacting?