So this happened last week when we were skiing. Before we went I was hunting around for my ski socks (basically very long, very thick socks if you don't know), asking my girlfriend to tell me if she'd seen any of them because I was sure I had more, but couldn't manage to get together 6 pairs (1 for each day). She said she hadn't seen any. Anyway, I didn't have time to buy more, so I figured I would either re-use them or buy more out there. 

On day 2, I see in my girlfriend's suitcase that she's packed what looks like the missing pairs of my ski socks. I'm instantly annoyed by this, because she has solved her problem of not having enough ski socks and just passed it on to me. I ask her - "are those mine?", and she says, "you left them at my house so I took them". We kind of leave it there.

Come day 5 when I have run out of clean socks, I go into her suitcase while she's in the shower, and put on my damn socks. She comes out of the shower, starts getting changed and is soon hunting around for some socks. She eventually notices them on my feet, and me with a big shit-eating grin. I foolishly thought this would be funny, we'd have a laugh about her obvious theft, and she'd go buy some more for herself. NOPE.

She gets very upset that I've put her in this position, that I've just taken the socks she was planning on wearing, and am expecting her to buy more or just wear an old pair twice. She gets really mad about it. I say she can just go buy more, but she says the shop socks aren't as good, and isn't happy about this. So I say "what, you think I should buy more? They're my socks!" to which she says "yes, but I packed them!". She seems really mad about it so to smooth things over, I let her have the socks, and I go buy more myself on the way to the lifts. They aren't as good as my old socks. Girlfriend is still annoyed about this at the end of the day, although she's calmed down now. Like, I get that she packed them and was planning on wearing them, and I took them, but I can't help but feel I've been fucked over here. 

AITA?