Confrontation in whichever form it is presented, is never easy. If it is making you upset/uncomfortable about addressing this with her??, then you weigh the balance of losing an obviously valued soap, or not making any waves and letting it go. However, since this seems like a new living situation my advice for you is to establish some boundaries early on. Since she is so easy to throw away something that does not belong to her, what happens when she eats food you may receive from home? - or borrows something of yours without asking?. Even though I LOVE the picture in my head of her dumpster diving for your soap, (and then needing to use it to get the stench off), I don't think you would have posted if this if it was your personality. How about during a quiet time in the room express your interest in soap making and how that bar was important to you. At the same time you can also tell her that you felt disrespected when she threw away something that belonged to you without asking. No yelling, no attitude. Normal conversational tone of voice but keep eye contact with her. Make sure you see that little flicker in her eyes that she gets it. Body language is more truthful than words. If in the happenstance she does not get it, be mindful of your possessions and spend some time with the dorm manager. Within 30 days students come and go and you may be able to make a room change. I do believe though that if you speak with her you will be proud of yourself for your personal accomplishment. Regardless, I am sorry for your loss. A comforting item from home as you spread your wings always makes the bad days a little easier.