Not that she should be riding on the sidewalk (she shouldn't), but the shoulder of a road--no matter how wide it is--is not a good place to ride a bike.
If it's a proper shoulder, it's slanted, which makes balancing hard (and tiring). Debris ends up there.
Not to mention, that there are a few SS individuals that choose a certain spot to "crowd" out the bicyclists. In those areas, it's safer for the bicyclist to ride on the sidewalk.
There is a major road near here where there seems to be a car vs. cyclist incident at least once every year, including some very severe lifelong permanent injuries caused on occasions. This weekend a car driven by a SS plowed through a pack and sent 7 cyclists to hospital. One guy was thrown 20 metres off his bike. According to witnesses the driver got out and started yelling that they'd been in the "wrong lane" (utter nonsense! It's a multi-lane highway and there's no "wrong lane" as long as they're not blocking the road!). That to me is the stupidest part - I understand being annoyed on a 1 lane road if a cyclist or pack of cyclists are blocking your path, but when it's a multi-lane road all you have to do is change lanes. That simple. I've driven past the pack before and I admit it makes me a bit nervous that I'll clip somebody, but honestly it's not that hard to just drive in the other lane until I've passed them. The thing is, the pack is respectful, they keep to one lane, and they ride together so they are very visible! I honestly don't understand how a car can hit them - it's clearly a case of cruising on the highway and not paying any attention, so I hope they throw the book at him. I actually had relatives who were in this very cycle club until recently, but I always said to DH I didn't want him going on these particular rides, just way too dangerous. Even the best, safest cyclists can't protect themselves from idiot speeding drivers.
Ironically, my husband as well as being a cyclist is also a mad car enthusiast who owns his own race car so he's not anti-driver, in fact bad/rude/dangerous cyclists annoy him more than anybody as he knows they give them all a bad reputation. That's why I loathe the driver vs. cyclist debates because most cyclists are also drivers, so it's not as if they don't understand!