As to experience with that bike, friend's wife has one and I started on a Sirrus, the men's version. Very nice bikes, very road oriented. I upgraded the snot out of mine, and by the time I started group riding it was a largely different bike. I found the mountain triple crank useless, and put on a compact road, which is not without its share of annoying issues.

And yes I rode group miles on it, 50 miles at 17-19 average speeds, right close to 2500 ft of hill climbing. Can someone do it? Yes. Can everyone do it? I have no clue, but I think its unlikely. I could hang with the group at the 17 to 18 mph average paces, but over 18 was in trouble.

And yes it had 23mm tires, but I honestly saw little improvement over the 25's I had on it before 23. Would prolly stop there, but realize I am a big person. May be different for her.