We were part of a group of friends living abroad. She was always quite hard work, lots of drama, but I liked her, she made me laugh and we'd shared this great experience that was important to me. Eventually the group split up as people moved away or back home, but we stayed in touch. A few years ago, we all travelled back for a reunion when one of us got married in the same city we'd lived in. Lots of emails back and forth about how excited she was to see me, meet my new DP, etc. Saw her at the wedding, all was normal although she was a bit sulky and complained about the food...
Then I think a couple of days after the wedding a group of us went for dinner to one of our old haunts and she was absolutely vile, to everyone- the waiters, my DP, even my friend's lovely parents who were paying for our meal! She alternated between sulkily staring out of the window and replying "nothing, I'm fine, just fine" and heaving epic sighs when we asked her what was wrong, flouncing out to yell at a waiter that it was too hot/our table was crap/the food was taking too long/whatever, making nasty comments about just about everything (the wedding dress,how long the marriage would last, people's jobs, anything) or just glaring in silence. It was so so terrible and awkward.
As soon as we left the restaurant my DP asked me why on earth everyone had fluttered around her pandering to her ridiculous jealous tantrum and told me how mortified he was at her incredible rudeness to the waiting staff. I started to make excuses for her then about half way through realised he was right and couldn't believe how we had all just sat there and let her behave that way.
I haven't spoken to her since. I'm sure she hasn't noticed though so don't feel guilty!