I ride with my engagement ring and wedding ring. My engagement ring isn't a monster, but it's not tiny either (.8 carat diamond solitaire). I have never had a problem with it fitting under gloves (it just stretches the stretchy part out) or causing me any problems while riding. The gloves keep it protected.
Just my take on the whole thing since I hadn't seen anyone chime in that she actually rides with a rock on! 
Emily
Emily
2011 Jamis Dakar XC "Toto" - Selle Italia Ldy Gel Flow
2007 Trek Pilot 5.0 WSD "Gloria" - Selle Italia Diva Gel Flow
2004 Bike Friday Petite Pocket Crusoe - Selle Italia Diva Gel Flow