Hi, and thanks for your reply. I have analysed it at some length, and it stems back to feelings of unfairness, unjustness. My mother was attention-seeking, I spent a lot of time mediating between her and my father to try and make things happy, whilst all the time thinking how childish and stupid their arguments seemed (and I was a child). My sister was the 'golden child' in our family, and got praised for her 'character' when her behaviour was almost exactly the opposite of what we were taught was good behaviour. So this does run pretty deep - it actually hurts me when I see someone getting a lot of attention for attention-seeking behaviour because I know I could do exactly the same and get the attention, but I also know it's not right - maybe there's some jealousy involved as well.
I have really struggled with dealing with this, and although I try to come up with some ratification after the event, this doesn't stop the gut, immediate feeling when I see it happen. I'm starting to think maybe I should just avoid being in the same place at the same time as both of them, but that would mean missing out on a lot of events. My boyfriend is aware that this is an issue, but he unfortunately sees her behaviour as a temporary thing whilst she's getting over her last relationship - I don't think that's the case.