Does anyone else have a really bad realationship with their sister?

My sister is the nastiest, most spiteful, hurtful person I know. Her behaviour is unacceptable, and she doesn't seem to realise. She throws tantrums, infront of anyone, doctors, shop istants, family friends. And all my mum says is she has good points. She buys presents, but my partner said I shouldn't accept because to her it makes her behaviour acceptable, and how upset she makes me. She shouted at me about how selfish I was about my planned wedding in Thailand- in front of family friends who had to leave they were so embarred. The sad thing is her 10 year old daughter is turning into her, and I am actually beginning to not like her too. I have a fabulous relationship with my family- especially when she's not around. She's 37.