I grew up dealing with this with my mom's family. My grandmother and aunts were constantly fighting and then calling everyone to tell them not to talk to the other person. When my mother was angry with her mother or one of her sisters, she never did the "don't talk to that person" deal nor did she let the fights trickle down to us kids, but my aunts did get their kids involved. Now, thier kids fight with each other and call around telling people not to talk to the other person - it's a vicious cycle.
I would politely tell your sister that you love them both and that you understand that there are hurt feelings, but that you would rather not be a part of the disagreement and therefore, will be talking to both of them. I would also ask that they not involve you in the disagreement and not ask you to choose sides.
I would politely tell your sister that you love them both and that you understand that there are hurt feelings, but that you would rather not be a part of the disagreement and therefore, will be talking to both of them. I would also ask that they not involve you in the disagreement and not ask you to choose sides.