10,000 honeybees is a small colony. At peak season, a colony can go larger than 75,000 or more. Besides, this was in the walls (a common occurance) and weren't really a big deal. Honeybees in the house will go to the nearest strong light or a window since their vision is polarized for navigational reasons. They're just fuzzy babies and wouldn't hurt this lady at all.
Unless, of course, she petted them too hard....
Another beekeeper? Nice to see someone who knows something about bees. (Three colonies in Maine.)
It sounds like they did not close up the cavity very well. If there is any opening, the remains (it is hard to get rid of all the wax and honey) of the old colony will invite any swarm to set up shop there.