Ummmmmmm..........if this is the commercial I saw, first:
The couple weren't bf/gf, they were husband and wife and if you remember, his hand her parents were on the steps of the building the couple were in front of.
Second, he was asking her to remarry him............
Third, this couple wasn't a teen/early-twenties couple, they were definitely around 40 at least from their looks and the looks of his/her parents (who looked like in their 70's)
Fourth, she wasn't "showing no interest" in the guy......they are married..LISTEN to the dialog instead of just what caught your attention.
Fifth, I do agree DeBeers has promoted a commodity that is quite a common mineral/gem on this planet as being precious and rare. If you honestly want a rare gemstone, buy a colored one...ruby, emerald, sapphire, etc. Of course, in these you have to purchase a non-enhanced one and a natural one, not one of those lab-created pieces of junk.
Sixth, gotta hand it to DeBeers.....their advertising works for them. This is much like the oil companies convincing drivers that they need premium gasoline for "ulitmate performance" from their cars despite the fact that the vast majority of cars cannot utilize premium gas properly (compression ratio too low), there is usually no better detergents in premium vs. regular (at least for the big brands......maybe for the el cheapo stuff), and just putting premium in a car that is set up ofr burning 87 octane gas won't do a damned thing for you except empty your wallet faster and enrichen the coffers of the oil comp;any faster (the octane booster costs on average a penny or two to raise it from 87 to 91).