If you ask her if she'd prefer a lab diamond or one from the ground, and she says ground, you have your answer. If you force the issue and insist on getting the lab diamond, you're the douche.
Why ask? Personally I just nerded out over the specs a bit, filtered for colourless and unflawed as far as the naked eye can see (i.e. you can get better but requires a specialist with specialist equipment to tell, so who cares, she's wearing it not collecting or selling it) and then went with the largest I didn't think would look silly (or alternatively that's within budget, whichever limit's tighter).
I don't really think there's an unbiased way to ask. 'Lab-grown or natural' makes the latter sound more 'real' and better. 'Ethical or blood sweat and tears' is obviously out. 'Lab-grown and technically superior for the same money, or natural and more flawed' is about the best I can come up with, but the former is just objectively the correct answer isn't it? I don't see how anyone could understand the question and answer the latter. There just isn't a reason to prefer natural, all else being equal, for an item of personal jewellery that you're going to wear?
Why ask? Because when I’m giving a gift to my wife, the main thing I’m trying to optimize for is her happiness. And the criteria that I consider most important may not be the most important to her.
I don't really think there's an unbiased way to ask. 'Lab-grown or natural' makes the latter sound more 'real' and better. 'Ethical or blood sweat and tears' is obviously out. 'Lab-grown and technically superior for the same money, or natural and more flawed' is about the best I can come up with, but the former is just objectively the correct answer isn't it? I don't see how anyone could understand the question and answer the latter. There just isn't a reason to prefer natural, all else being equal, for an item of personal jewellery that you're going to wear?