Honorific term used to refer politely to another person's daughter. Not used for one's own daughter.
お宅の娘御はおいくつですか。
How old is your daughter?
社長の娘御が来月結婚されるそうです。
I heard that the company president's daughter is getting married next month.
Compound of 娘 (むすめ, 'daughter') and the honorific suffix 御 (ご).