["My mother in law does not know how to mind her business, I don't understand why she has to be so undermining to us.", 'What a jerk! Why is she always in your biz?', "I don't think she has any idea how nosy and irritating she is.  She continually will tell our girls how their father and I are doing things wrong."]
I would get up in her face and show her who's boss. Break out the broom and crack it across her old, measly back!
My mother in law does not know how to mind her business.  She continually tells my girls how their father and I should do things