i have a half sister who is 20 years younger than me, all she has done is look down her nose at me and make comments for example suggesting i am illegitimate, or snidy comments about how 'posh' my mum was, or comments about me being an 'unmarried mother', most recently she called me a 'cunt' to my children - well ok fine but for some reason she likes my daughter who she describes as her 'niece' even though my brother and I have heard several times over the years how we are not related to them - so that is a bit odd as surely a 'niece' is the child of your sister? and has these long private chats with her on fb, quizzing and questioning any of our family plans. it makes me irrationally angry, AIBU?