I'm starting to really dislike DSD1 and feel crap about it. I need some perspective and advice.
DP and I have had a couple of rough weekends with the DSCs (I posted about it on here a little while ago) - DSD1 causing lots of punch ups between the siblings, disrespect to both me and her father on top of the usual-to-be-expected-pushing-the-boundary behaviour typical for a 12 year old. Last weekend there were a few incidents that in isolation would be inconsequential, but it pushed me over the edge to the point where I can't stand the sight of her. It's totally out of proportion - she's not done anything dreadful, just an ongoing total lack of respect for me and DP, and it's rubbing off on the 2 younger DSCs.
Part of the problem (my problem) is she has the type of personality that winds me up anyway; always jostling to be the centre of attention, overbearing (bordering on bullying), and she always has an agenda, with the negotiation skills and the tenacity of a bulldog that would put the best barristers to shame. Everyone says she's always been like that; hard work but very bright with a big personality. She drives DP up the wall, and he does discipline her as well as having the important heart-to-heart conversations with her, but the effect wears off after a couple of hours. He tells me to look on the bright side - she's not evil (true) and there is no doubt she is going to be successful in life (yeah - if she hasn't pissed everyone else off along the way). Great! So only another 6 years to go then 
What to do? I spent this weekend more or less ignoring all the kids, leaving DP to it while I got on with my own things away from the house. I know this isn't sustainable and it's not what I want. I'm supposed to be the adult here, but she is really trying my (and DPs) patience.