Is it wrong that I avoid my sister?

My sister and I are half relations. Each having a different father we were raised by hers. A rather dysfunctional man he exhibited traits of his family's legacy mental illness (a sort of mix of bipolar disorder with that of a borderline personality issue) and was very difficult to live with. Not being his son I was relegated to a low spot on the family totem pole and could be said as having been abused by him. My sister, displays many of the same symptoms he always did: uncontrollable crudeness, a drive to forever be the center of attention and a generally chaotic way of going through life I find it hard to be with her. There's more to it than that. But, suffice it to say, she and her father share a lot in common. Now, I find myself practically running when I see her on the street and trying to avoid her at whatever family get together there is. Personally, I feel as though that man's family and its mania was rather put upon me. Having she have the same issue opens a lot of wounds up for me. I do see to it that her affairs are taken care of: paying for her yard maintenance and footing her heating bills and the like, I'm not a derelict brother. But, I just can't be with her. Is that wrong or understandable to you?