OP, I'm sorry to hear about your situation. You're not alone in family struggles. It must be so frustrating for you to talk calmly with your sister about the 'good' things you did for her b/c she only remembers the bad.
My dad is a very deceptive person and makes up stories in his head that my mom is the reason he's in prison (he's in for insurance fraud not pertaining at all to my mom but his personal business). He was a very hurtful parent who gave conditional love (if one even can call it 'love') and has caused havoc in our lives. He's battled substance abuse, tried killing himself in our home about 4 times, attacked my mom twice, and pushed my older sister across the room. We had to call the police on him when he was on house arrest and he went straight to prison and then was sentenced to more prison time. It continues to haunt all of us what went on and how my dad still upsets us in phone calls and letters.
So anyway, back to you -- one piece of advice is when your sister goes on about you being a not-so-perfect sister, maybe a comment like, "You know, life was very hard for me back then, too. I'm sorry I hurt your feelings. You have to remember I was a young girl with a hurtful mother. And when I learned better, I did better." My sister is a few years younger than me and my dad was worst on her verbally. As a kid, I wanted to be on my dad's "team" so I would tell my sister what my dad said was true about her (telling her she was loose or whatever). I look back now and realize I was afraid of losing my dad so by teaming up with him, I kept him but hurt my sister. Also, I was brainwashed to think people who were a bit premiscuous were 'bad people.' A therapist told me to tell my sister that she should remember I was going through an equally awful childhood too and that I'm sorry I couldn't have been there for her. While she was in her pain I was in my own pain from having the same, hurtful father. We were all trying to cope -- and still today we are. It's been very hard on our family and we continue to struggle with dealing with my dad and it's been a solid 10 years since he got into the stage of being completely irrational.
I guess I don't have any easy advice b/c I've seen that things can resurface from the past. I've found that one statement above to be helpful, but know that all efforts you do to make things better do help a bit here and there. There's no easy solution, but something is always learned. I wish it were easy to fix things, but often not.
Again, I'm so sorry for your childhood. What a very hard life to care for a baby sister, sick mother and attend school. You should be so proud of all you've accomplished.
