I think you did what you needed to do to make your mental health better. I would have found emailing her to say you no longer wanted contact unnecessary since she wasn't contacting you but I think it is what you needed to do for closure, to let her know that you have finally let go of this relationship and the need to understand what is wrong. but I think you are looking at this wrong. you didn't do anything wrong. you did what you needed to do for your family. this is your sisters problem. she is punishing you for it. she is being childish. she refuses to communicate. this is all on her. unfortunately you lose. this doesn't mean you have to stop sending cards for Christmas to her kids. why would you punish them for what your sister has done? just because she chooses to be a ***** doesn't mean you have to. but if it hurts you too much to have that contact, then certainly stop.