Oh wow... I can see why you were so taken aback. Em, that is just... divine. That is all I can say about it. Divine. It would be beautiful on your back between your shoulderblades to remind you that even though you can't see her anymore, she is always watching over you.
And I get the grandparent thing. My mother wanted me until she got me and then... not so much. My Mammaw is the closest thing I will have to a mother and in my eyes, she is. And it sounds like your parents are regular parents of the year, so I know living with them is like nails down the chalkboard of your soul.