Translation:My great-grandmother knew how to sew dresses.
Just to make this clear... povi is to be able because you have the ability, scipovi is to be able because you have the knowledge, and rajti is to be able because you have permission?
kapabli = to be able to but not necessarily have the posibility
Mi kapablas ludi pianon sed nun ne povas, ĉar ne estas piano ĉi tie.
"Could" should be accepted since it can be used to express ability in the past.