I'm pretty sure she meant 20 degrees F. She rides all winter...
I build up my tolerance for cold in the fall and early spring, but I tend to wear too much if it's cool in the summer. Mostly I layer with arm warmers, vest, maybe a base layer, wool socks, etc.
I could never wear shorts at 48 degrees. It has to be close to 70 for me to wear shorts. Usually I'm in knickers or knee warmers between 55 and 70.