Hehe, I am a sag mom with bull headed (Taurus) daughter. I know your sister may be an adult, but your mom is still the "grown up" and negotiate a resolution. If she is not yet an adult, it just strengthens my point. Your mom being a Sag will probably figure that out for herself. In the mean time convey yo each that you value them and family harmony and have faith that they can figure it out.