Miss.
"Young, Lady" or call her by name.
Misses or Mlles
Mademoiselle is French for "miss", the formal address for an unmarried young woman.
Depending on how young the girl is you would be more informal with her. You address her with "du" and say "Hallo" instead of "Guten Tag".
Was the Gettysburgs address was written in formal English
i think a child.preteen ages are 11 or something. <><><><> The formal term of address is Miss. As in Miss Julia Brown, age 9.
When addressing letters to juveniles, you can use "Dear [First Name]" as a formal and friendly salutation. Avoid using terms like "Miss" or "Mr." unless the juvenile has expressed a preference for a more formal mode of address. Remember to be understanding and compassionate in your communication.
Formal
Be very formal.
Any age as long as they're not married ... if they are married then you call them Mrs.
I've only seen this one time before, and it is a very formal way of addressing correspondence to a young male. "Mst" was the abbreviation for "Master," an old-fashioned term of formal address for juvenile males.