If it were mine, I wouldn't add a border, just a pretty color for the binding, or a white. I think a border might distract from this beauty. I think any color you want for the back since there are so many pretty colors in this quilt. I know were you are with that horrid disease. We lost my Dad to that terrible monster, and I've lost some friends to it as well. Keep your chin up, and just give her lots of hugs and love, try and not become angry with her, because she is not aware of what she says or does. Just remember she needs and will as time goes by, lots of loving care- just like she gave you when you were growing up.Prayers go out to all who have a loved one with this dreaded monster.
Perhaps the quilt when finished will spark a memory for her. What a treasure you will have when it is finished. Love and Hugs to both of you.