How is she that clumsy? Glasses don't actually fall that easily, except hers I guess

Say that to someone who had to buy new glasses for $800 USD because their glasses fell on the floor as she was looking down . . . . now I wear a chain attached so they don't get far when they fall.

I find that certain brands stay put better than others

I concur. (As someone who wear glasses, play basketball, jump into the river without taking off glasses, etc.) Sis really needs to find other glasses or other items that will stay on properly.