My husband has been in Senior care for many years.
We often have taken the children to visit residents in the memory wing. We have found simple things bring them temperarily in to a lucid state and their memories are so vivid. See if there are any fabrics or clothing items that may have been special to the grandma that may be of comfort to her to use in the quilt. Items like that are more comforting then something made all brand new. Do put her name in a very obvious place on the quilt for two reasons- ownership ID and for her to see her name. Using a premade comforter for a backing is not a bad idea as it will give more of a gentle tactile feel for her. Also be sure to clarify with the staff that all care for the quilt will be done by family. Also keep in mind that she may be experiencing bathroom mishaps and an expensive quilt may not be the best choice as the timing of your picking it up to launder it may be must past the middle of the night accident.