Woman: Solitaire setting is the most classic and traditional route you can take when setting a diamond. Here, I have, a plain setting that doesn't have a diamond in it yet, just so you can see the bare bones. This is a four prong basket head best suited for a round stone. As you can see, the four prongs protect the diamond, and it just has a little bit of pave on the side to enhance the look of the ring.
A Solitaire basically means just one stone, one solitary single stone. And, that's what you want the emphasis to be on. So, Solitaire can be just plain metal or can have a little bit of stones accenting it on the side, or, underneath the diamond, as in this one. On the sides of this asscher cut, or, around the center stone of this cushion cut, with the halo. They're so many settings to choose from.
If you're not sure, it's always best to go with the Solitaire setting. That way, you can change it down the road if she wants something a little bit different. Remember that you want this ring to last for a lifetime. So chose something that is timeless and elegant.