I am sorry you have to hear things like this from your sister when you both go through the same do you think its her illness that makes her say such thing ( if she has an illness? )

I would not think that is an excuse because I think she must be aware that she acts differently when with family.

My sister, before we got much closer ( we didnt spend any time together like 15-20 years ago ), she acted differently against me when together with other friends ( not so good friends I would say ), but nice and acknowledging me when alone with her.

I think she had a strong need for attention before ( she has grown too ) and needed to be in the spot light. I do think she was aware of acting differently but I have never asked her or said this to her. That she did this before. She could smile and cheer with everyone around the table but chose to ignore cheering with me.

It makes one wonder if they are aware they do it but I think they must have. I really dont know. Its weird.