I had a situation with a university friend of mine that was so minor but pissed me off a lot. This girl is from my university, we have known each other for over 3 years, worked on most projects together and went out from time to time (she's not really a social animal).
So today me and another friend of ours went to the cinema, it was all fun and stuff. She always drives us home and it was late so that's what she was going to do today as well. My other friend lives closer to the cinema, so it was the first stop, but there they had to go upstairs for a minute because she had to pick something up. So we were almost there and I was like "alright, I'll just stay downstairs and wait for you" and she suddenly went serious like "I'm not letting you stay in the car". I thought to myself - what the fuck did you just say? I said "I'll wait outside, I won't break in so don't worry about your windows". It was so ridiculous to me and I still can't believe that shit, it felt like betrayal. After all those years trust is the least I'd expect. She came back and drove me home like nothing happened.