How do you tell your sister-in-law to leave you and your husband alone when in an argument? Mine is very intrusive and I need to put a stop to it. Please advise!

Don't argue with your husband infront of anyone. I argue with my husband in private. when we're out in public, I try my best to not mention anything we argued about. Always, we end up reconciling because we forget what we argued about in private...and it gives us a break.