I get sick and tired of all the "stuff" periodically. I purge and then do machine embroidery, garment sewing, home dec. I eventually quilt a bit as I like to visit with quilting friends in the States periodically, and they keep me at it. I have a short attention span and large projects, while I love to start them, end up as UFO's.
Your mom may just be tired of all of it. My 85 yr. old mother loved to sew. She doesn't anymore. It's too much for her. She will knit a bit and embroider. I think sometimes our interests and physical abilities change so we do different things. If your mom wants to stop quilting and sewing, let her. Your thoughts of putting some of her stuff away to save for her is a good one, for the time being.