Hey, give a girl a ring to "symbolize" a marital arrangement, and if it sparkles, it's a GIFT, not a SYMBOL, maybe even a BRIBE, after all.
I do believe if she wears a plain, gold band to that meat-market of a gymn, it's far better horn-doggie repellant than a diamond any day. "Oh, honey, I just left my diamond wedding ring at home because I didn't want to damage it during my workout!" Really?
And those, er, IMPLANTS she very sweetly demanded that you pay for, saying, "because they're all for you, baby!"?
I say, give her a few gifts of diamonds and gold BEFORE the big day, but to symbolize a standing betrothal, it's a plain, gold band, dude.
Unless you're just afraid she thinks you're not worthy...
...then do the sparkler. $$$$$$$$$$$ =
"The curse of being wise is that nobody listens."