Hello Steve,
Yes, I've gone through this. It is much easier when two siblings are on the same page.
Does it feel that your sister's different view of the situation invalidates your own perceptions? I see that you want her to accept your view but you do not agree with hers, especially about your mother. Yet, her experience may indeed have been very different than yours, and she may feel equally invalidated by your statements of your reality. Frankly you are both entitled to feel however you wish to about your OWN perceptions, for that is YOUR reality. In the spirit of love, you must come to accept that you and your sister each have a right to feel however you wish!
Awen, you hit the nail on the head. I added the bold because this is the crux of the matter. Steve, your father may have treated you the same (not a given because some Ns deliberately treat sibs differently), but let's say it was the same. Different sibs will respond differently.
I have two brothers and for some reason I do not understand, I could not listen to one brother complain about my father even though I agreed with him. I think maybe it was because he wanted me to fight his battle for him. And that's what I resisted. I told him not to put me in the middle. I also resented his statements because he married someone who was just as bad if not worse who was causing a lot of problems within the family. So his criticism of our father was just to ward off the crap headed in his direction. Also, even though I agreed with the assessment, I wasn't ready to take on my father. It was NOT in my best interest to head into the breach. I very much resented the treatment my SIL gave my father because basically she was communicating the message that she was more important and she was now the head of the family, not him. I didn't remember voting for her to be the boss of me.
As for the other brother who I could listen to because he had been fighting his own battles without involving me, he couldn't buy the fact that I was treated badly for being a girl. Because this meant my battle was somehow unique and special and so had to be discounted. He didn't buy it until my father pulled a really disgusting and degrading move recently which I won't go into here. I told this brother about it and he was just shocked. "I can't imagine Dad doing that with me," he said. I said "do you get it now?" meaning my dad's low opinion of women. So our experiences of our parents will be unique to each child.
I don't know if this applies in any way to your situation, but this is part of how it was for me. I'm guessing you want some insider support for your position. This is really something you have to wrestle with on your own terms w/o sis. If you are troubled by her response (you're being selfish, etc) you can try to explain your position without trying to change hers. Something I hang onto re the charge of selfishness is that it isn't selfish to take care of myself. It isn't selfish to have needs and think of my own emotional survival. Hopefully you are not being deliberately hurtful of your father, but just taking care of yourself.
Hope this helps. Good luck, MP