[I'm still emotionally charged over this, so I'll do my best to stick to the facts. I'm looking for advice on how to handle this going forward, or hearing about what you did in a similar situation.] Recently, my SO and I went out of country for a few weeks. Right before we left, one of our cats had an allergic reaction and needed to be medicated twice daily while we were gone. We changed our plans of having a friend stop by every couple of days to check in on the cats and instead asked his younger sister (18) to house-sit - it was convenient as she needed a place to stay for a couple of weeks before moving into a new place. We bought a bunch of groceries for her as well as leaving her some bus tickets and cash. The only restrictions we gave her were to always lock the doors and not to bring any friends over. We didn't want anyone other than her in our house, mainly because there's a bunch of business equipment that's expensive to replace and we don't trust her choice of friends. We returned without incident and the cat was and is now just fine. However, shortly after she left I noticed that my clothes had been rearranged. On further inspection I noticed a number of clothing items missing, including several with sentimental value to me (she would not have known about their value). The number of missing items is high enough that it was definitely not an "oops, I accidentally packed your shirt in my suitcase" scenario, and somewhat disturbingly included several pairs of underwear and a bra. I don't buy clothes often and I choose the ones I do buy carefully, so it was probably more upsetting to me than it would be to many other people to experience this (especially since I've never had sisters or girlfriends with whom I've shared clothing in the past). To discover it without prior explanation was quite alarming. To give her some background, she's had a tumultous upbringing. Her mom wasn't able to discipline her effectively and the household was dysfunctional, so she got used to doing exactly what she wanted to do at a young age. Her first real taste of discipline came when she lived with my SO for a year when she was ~14 (before I was in the picture). He would set boundaries and follow through with punishment, unlike what she'd experienced at home - the "if you go out when you're grounded, you will not be allowed on the internet for a week" sorts of things. It did her some good and while she hasn't completely straightened out, we figured she'd at least matured to the point where we could trust her to house-sit. However, as mentioned earlier, we don't trust her judge of character when it comes to her friends. In the heat of the moment, I sent off an email which basically said "Please return my missing stuff - it's bad enough that you wore them without asking; if you lent them to your friends you were way out of line. I felt betrayed that you didn't ask me first. I'm annoyed that some things are now stained and missing.". The tone of the email was definitely "I'm pissed off", although it didn't contain any profanities and I was careful not to attack her personally. I did not follow the email up with any further contact. I didn't hear any response until today (which is about a month after the fact) when she sent back a response which did nothing except show her immaturity - direct personal attacks and no response to the actual substance of the email except to say that she "would only wear your clothing to bed" and to "ask before you acuse[sic]". So, it's evident that we missed the mark in assessing her emotional maturity. Because I'm so anal about my clothing, I know for a fact that each of the items now missing were there when I left. It helped that I'd done all of my laundry immediately prior. No other items of value appear to be missing - there's plenty of computer equipment that would have gone missing had the place been broken into and no one with that mindset is going to find my underwear valuable. Since we'd told her in no uncertain terms not to bring people over, she's either brought friends over who decided to help themselves (with or without her knowledge), or she's taken them herself. Either way it doesn't look good for her since she was supposed to be responsible for looking after the place. Now that my shock and indignation has mostly died down, I'm left with a number of thoughts to reflect on: First, although I don't generally classify myself as materialistic and I think (hope!) it's mostly the principle of the thing, should I be getting "wound up over a bunch of clothes"? My thought here is that I'd replace them as I could and simply take the replacement price out of the budget that would buy her birthday and Christmas gifts, but she'd be missing about two years' worth of gifts if we did this - I don't think I care to drag this out that long; principle or not they ARE just clothes - and that doesn't address either availability of sentimentality. Second, how do I go about repairing a relationship with her? We didn't have much of one before (mostly due to location and lack of contact - we live several hours apart - but also due to the age gap). I already plan on having my SO call her to clear it up; he volunteered to take care of once he realized that the missing stuff had to have been premeditated in addition to other signs pointing towards her having friends over (it was his idea for the no-guests rule since most of the aforementioned equipment is his - he works from home). That doesn't help me with the aftermath though. Whatever the outcome, she's likely to be bitter at being cornered no matter how much she may deserve it. I'm frustrated and I know that I'm at least partly in the right, but I can't help but feel like this whole experience is one big losing battle. Any thoughts?