I think the sister is being controlling because by saying that you are “controlled” and have to “hate” her because of your husband! That is very manipulative. This is not an intervention on behalf of a controlled woman. This is so she can be friends with one spouse and still fight with the other!

Asking one spouse to go against the other (even in support) is over the top. She can’t have it out with one, so she goes for the easier target! Don’t be the easier target.

Just say, “I want peace in the home” or “I’m not discussing this” or “You’re not over that yet?” when she brings it up.

And, on another note, of course you can be friends with her! Just don’t have it be in your husband’s face! Don’t hide or deny it either! Be all, “Honey, I want peace in the home”, “I’m not discussing this” or “You’re not over that yet?”

The decision is ultimately yours, but I would let your husband handle it and take the lead.