Some hens don't get up after day 18 or 19, but most of mine do, they just don't stay off of the nest for more than a minute or two at a time though... usually just to get a drink maybe and do their broody poo away from the nest. We give our broodies a small dish with food such as scrambled eggs or chopped cooked fish, mixed with seeds or chick starter... this allows them to snack a bit without getting up, and water is always close by.
Her rolling the eggs is more likely intentional than clumsiness, the hens will frequently rearrange the eggs in the nest to aid in regulating their temperature and development rate. I have video of our silkie doing so 3 or 4 times a day (think spy camera! LOL). The hens don't seem to have problems with the positioning thing and in the last 40 or 50 eggs we have hatched in the past year with broodies we haven't had any pip at the wrong end and fail (never found one dead in a shell pipped at wrong end at least)