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!