she wasn't likeable, she was so very angry for no reason - just one hell of an angry kid. she banged doors stomped up the stairs, beat her twin brother up...she had ishoos man .
i didn't focus on it as much as your doing - becuase i have 2 boys as well and if she went off on a tant, i had better things to do than waste my energy.
its all attention seeking.
she was trying to make her existance known.
i honestly think the way to go is ignoring her. and tell her straight that mummy isn't entertaining her until she can be nice.
kids ned discipline - so dont beat yourself up about the discipline part.
my DD found her groove at school, being more intelligent than her brothers, having her own friends becuase her brothers played together an expluded her becuase she was a girl so once she got into the throws of school with school friends and school work - she found her niche and has been great ever since.
good luck.