It was her quilt, so I would finish it the way she made it - you will always treasure that quilt, not the fact that two adjoining blocks are the same color. I seriously doubt that anyone will notice.
Your first instincts were "spot on". I aged with you & the majority. Leave it as she made it & quilt it. It's very pretty & I'd like to see the finished project!!
If I had made it, I would probably take it apart and redo it. If someone special to me had made it, I would leave it as is. That way every time you see the "mistake" you will think of her.