Thanks to everyone for your input. Unfortunately, sitting down to do the fake shopping thing isn't an option. She'd know in a heartbeat what I'm doing. She didn't drop that "I deserve a big 'ol Moissanite for my anniversary!" in my lap by accident. She knows that I'm the one who will light a fire under the boy and get him to do it. If I never let on that the boy and are in cahoots, she'll be curious but probably assume that nothing came of it. At least that will preserve an element of surprise and make it more gift-like.
Yes, she for sure wants an upgrade wedding ring, not a RHR. And it's an enthusiastic want, not an in-passing idea. I think it took her a long time to believe that she deserves the luxury, and now that their 25th is upon them, she got past her mind set that such indulgences are only for other people.
I do have a good sense of what she does and doesn't like, since we've been friends for more than 25 years. She's very practical but has flair -- for instance, she packed her kids into an old used Grand Prix to avoid driving a mini van as a mom, and she has simple home furnishings but painted every room with fun colors for personality. I feel good about the options I've narrowed down for her, but it's so hard to commit to saying, "This is the one" when it's something SO personal as a wedding ring.
Here are the settings that are on the table right now. Everything fulfills her needs of a) low and/or gradually set, b) no melee for durability, c) not too busy or flashy.
The boy likes this one: http://www.moissaniteco.com/low-set-round-moissanite-solitaire-ring-p-8246.html
I like these three best:http://www.moissaniteco.com/65mm4mm-round-brilliant-moissanite-3stone-ring-15ct-p-11730.htmlhttp://www.moissaniteco.com/double-prong...ing-p-8219.htmlhttp://www.moissaniteco.com/round-moissanite-half-bezel-bypass-solitaire-ring-p-9101.html