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!

Heyi don't get it...how does she interfere with her opinions? How does she know whenever u guys are discussing/having an argument? Don't tell me she lives with you guys??? Also is she asked for her opinions or she just feels the need to intervene You have to figure out a way for her to stay away from both of you when its not required... From your question I gather that she's overall a very intruding persona... Politely smirkingly tell her a couple of times and thats it... Then be direct and ask her to back off if she still doesn't get it... Keep your wife on your side so that she doesn't take offense to this..