It is hard to understand. Very hard. I understand that. But you can't change what someone else did (or didn't do). You can't change your mother now either. You can't change your own past decisions either, but if you could, would you want to change these things? Would it have been worth it to act like your sister did? Who would you rather be now - her, or you? You don't have to be a victim anymore, and I do understand how hard it is to stop.