Okay so, context. I, (26M) have been with my girlfriend who i'll call Maddy (also 26F) for five years now. I also have a sister who's still in high school (16). Whilst we have a huge age gap I love my sister. I'm afraid I spoiled her a bit growing up but yeah i'm her big bro, that’s pretty normal. Anyway, Maddy found out in 2023 that she has alopecia universalis. Her hair started falling out pretty dramatically since she had long hair, and she was really embarrassed. I know some assholes care about the vain stuff like that but I don't, i’m not a saint just a normal guy, but I saw it embarrassed her so in the autumn we both buzzed our hair together. Pretty soon after she started buying some normal and real hair wigs to test them out, and loved them. They are not cheap by any means but she feels confident with them so it doesn't matter to me. Maddy has met my sister, who i'll call Helena, a lot. She always wants Maddy to either take it off and show her head or give it to her. She even tugged at it once (it's glued on so didn't budge) and was mad it didn't come off. I got mad but Maddy laughed it off, not wanting to cause a scene. We saved up and went away to this nice hotel on a Greek island, and got my sister to 'flat-sit' when we were on holiday for some extra cash. Half-way through the trip I got tiktoks of my sisters and her friends in OUR ROOM wearing some of her wigs and lip-syncing some audio off of dance moms. I was pissed, admittedly first because they were in our locked room, but then because of the wigs. I saw they cut one of the very expensive blonde wigs into a short pixie. I showed Maddy, she seemed shocked but brushed it off, saying it was fine and she'll get more. I texted her to stop, and if I catch her doing it again she'll pay for a new one. She ‘apologised’, said they were just having fun but they'll stop. Nothing else happened so we forgot about it until we got back. We reached our room, she opened the cupboard to where she keeps her wigs and they were haphazardly shoved in, cut, and some of them dyed. I was shocked. One of her wigs had been badly bleached, then dyed pink and was practically hay. I was beyond pissed off. I was beyond furious. I immediately call her, and she doesn't answer, so I call our mom. I tell her what Helena did, chewing her out. Telling her she was disrespectful to Maddy and she needs to learn how to respect other people. Mom was shocked because she knows how expensive they are, but also said she's just a kid and doesn't know better. Then offered to pay. I said I would only be satisfied if Helena payed Maddy back. She told me I was being dramatic and told me to 'cool down'. Maddy heard this and told me not to worry. It's just material and she was upset but knows my sister didn't mean it. I swear she's an angel. That's the thing tho, she’s really smart, I wouldn't expect her to be so stupid, I wouldn't be surprised if she did this on purpose. Am I the asshole for wanting her to pay my girlfriend back?