My good friend, Andy, wrote a little question for me in one of the comments:
Is it actually possible nowadays to make a diamond from the carbon of a deceased loved one?
Yes. Here's a link to a company that does just that. Not just for humans but also your pets.
Also, if you're willing to burn some cash (VERY expensive!!) , they can do it with a lock of hair also... so a very very traditionally romantic gift can be made.