。
When did your daughter come of age?
Literal
Daughter [topic-は] when honorable-become-adult [past-polite-ましたか].
娘さん uses the honorific さん for someone else's daughter — polite way to refer to another's family members. 成人する ('to become an adult') in sonkeigo (honorific) form 成人される — the ~れる honorific form applied to a する verb. Asks politely about another person's family milestone.