The Ruby would be a great bike (that's what I ride also), though somewhat pricey. The carbon frame does dampen a lot of unpleasant road vibration. The Trek Lexa, the Dolce, Cannondale Synapse are all good road bike choices.

I'm just a few years shy of your mom's age. I went from a heavy comfort bike to a Cannondale Quick 3, which is pretty nimble for a hybrid. I had to move up slowly - the jump from a comfort bike to a road bike was just too uncomfortable and strange to me. Perhaps one of the flat bar road bikes like the Quick series might do the trick. I've done upwards of 35 mile rides on that bike, and it's great for MUPs and rail trails too. When I decided to move up to a road bike I wasn't finding the aluminum framed bikes a heck of a lot faster than my Quick 3. Wasn't til I got into CF frames that I found what I wanted in a road bike.

As a total aside, my adult daughter rides just a hardtail mountain bike. She's used it in triathlons and on 50 mile hilly rides in Maine and NH. And she kicks my a$$. I would love to get her on a faster bike, but she enjoys the workout the heavier bike gives her.