Long story short, my stepsister doesn’t have a job. Recently, I started noticing that she was using my expensive shampoo without asking. I told her to stop. That’s when my stepmom rushed to my room and blew up, “You are so petty and selfish!”

So when she left, I secretly arranged all my shampoo and conditioner into a locked box I keep in my closet now. After it, I added a cheap brand to the bathroom shelf.

When my stepsister found out, she said, “It’s just shampoo, why are you making it a big deal?” I told her that if it’s just shampoo, then she can buy her own. She rolled her eyes, and now they are both mad at me. My MIL complains to my dad that I’ve been treating her daughter like a total stranger, while family should always come first.

My dad told me to apologize “to just keep the peace,” but I don’t feel like I did anything wrong. I buy my own stuff with my own money, and she doesn’t even ask! I don’t really think it’s fair to call me selfish for that. So, I’m sitting here wondering what I should do next: unlock my shampoo and let my stepsister use it just to cool things down, or stand my ground? Please help.