The dynamic with your sister will not change unless you make it change by limiting your contact with her.

This would be a great question to discuss with your therapist. I bet it has a lot to do with how you were treated in childhood.

I agree with Divine. Do not ever go on "vacation" with your sister again. Don't explain why, that will just lead to another argument. Just don't do it.

Definitely use "grey rock". Neither you nor your husband should try to explain things to her, or reason with her. Simply minimize contact and don't engage in any disagreement with her.

It doesn't matter that she raised you. That doesn't give her the right to mistreat you and your husband now. She isn't your mom and she isn't your husband. You don''t owe her such allegiance.

It's possible that your mom will lean on you to go on vacation with them again. Don't do it! It's possible that your mom will side with your sister, so as to have more joint vacations. She is your mom, but your first allegiance is to your husband, and to yourself! Therefore, work on self-regard and boundaries with your therapist. Put yourself and your husband first!