She described what she wanted exactly– nothing gaudy or ostentatious, just a singular, tasteful stone on a plain band. Couldn't be simpler, could it?
Finding stones that met her criteria was easy. Some were natural diamonds, some lab grown, many moissanite. From the outset, she said the meaning of the ring was what was most important and that she didn't want to pick it out herself (after effectively picking it out herself). We'd talked about moissanite a lot over the years, and she'd approved of the idea, and the same with lab grown diamonds. We're college educated adults with backgrounds in the sciences, so we weren't on uneven footing with comprehension.
When I showed her what I'd picked out, it quickly devolved into a lot of uncharacteristic tears and shouting. It took a few more tries, and then she explained. Apparently a lab grown diamond meant my love for her was also artificial, a budgeted ersatz stand-in for the real thing, and me saying we could spend more on a larger stone or matching set further belied my ignorance. No, she wanted me to have picked out an allegory for our love: a "perfect" diamond. She then sent me the details of the stone she actually wanted.
After a little "wait, where's this coming from and why did you let me spend weeks searching if there was only one right answer", I ended up spending twice our decided budget on a "natural" diamond with the same characteristics as the lab grown (except the diamond's clarity was lower, because lab grown clarity is always perfect), which wasn't any object, but now the ring is marred by the memories of arguments, and she doesn't really love it. Lesson learned.
I don't know what kind of spell the diamond people cast on otherwise reasonable women to make them able to reduce the totality of a life and experiences shared together into a single crystalline bet, but they need to package it and sell it to the military.