Hello, dear friend!
I haven’t spoken to you for ages. How are you doing?
In your last letter you asked me about my best friend. She is a very nice girl.
В следующем абзаце, опиши внешность твоей подруги, потом ее характер
Концовка:
And what is your best friend like? I would like to know something about her.
Yours sincerely, /твоё имя и фамилия/