I bet if Kevin had proposed to Whitney (in another universe/timeline/plane/whatever) and given her a vintage ring, and they showed up at a red carpet and Joan Rivers tried that mess, Whitney would have shut Joan down.

Joan Rivers: Good evening, guys. You look great. Kevin Costner and Whitney Houston, everybody. Get to making ridiculously good looking babies, already, would you two?
Whitney: Ha, ha! Girl, you crazy!
Joan Rivers: Let me see the ring.
Whitney shows it.
Joan Rivers: Oh my G-d! I need my prescription glasses to see that puny thing. It's so tiny. And where is that cut from? Van Cleef & Arpels? Tacori?
Whitney: Um, no. Joan.
Joan Rivers: Harry Winston at least? Michael B.?
Kevin: None of the above. It's classic vintage art deco. From the 20s. It's an estate piece I found while we were in—
Joan Rivers: You couldn't even spring for Tiffany, Kevin?!?! What a shame. It makes my daughter's ring look like it just had a baby. You could have done better than that for a superstar.
Whitney: Well, I didn't ask him to clean out his wallet, Joan. That's not even necessary.
Joan Rivers: Honey, we all know you love to stand by your man. In the case of your last marriage, a little too much. But this little ice chip in a tin band is not up to par, Whitney.
Whitney: You know what Joan, we're not into being flashy. Anyway, I had a bling-bling engagement ring on my first marriage and look what that got me. I think it's better for everyone, including you, to try to be tasteful.
Kevin: I tried to warn you, Joan.
Whitney: Like your makeup for instance, Joan. It's a little sharp and shrewish for a woman your age. Instead of worrying about the rocks on people's hands, worry about what all that Botox and face-stretching is doing to your personality. Oh! I see Quincy (Jones). A man with real class, which is much needed right now. Let's go, baby.