I read the article. Was the fiancee (woman) complaining about the style of diamond, or the size/value?
I don't know much about diamonds, but the article said she wrote, “Ewwwww. Self shame Friday here I come,” she wrote. “Found this in the BF’s nightstand. Not a fan.” and asked how she can ask the BF to get different diamond. That makes it sound like she didn't like the style, not that she thought it was small. The article suggests she posted at a "ring shaming FB group". I don't know if that group shames size/value or style. I have no idea.
Do people actually dislike a diamond cut? I mean I know there are different cuts, but could she really be that repelled by the cut, which I would assume would be a standard cut? Or am I being naive, that of course she was talking about the size/value?
If I thought my fiancee wanted a diamond ring, I think I would borrow one for my proposal, and if she said yes, I'd have her pick one out herself, as she's the one who has to wear it. I would hope she wouldn't desire a wealth status symbol on her finger, and otherwise feel shame about the size, but I'd want to know, and we'd work something out, or maybe not.