pronoun
your older sister
Honorific pronoun used to refer to the addressee's older sister, mainly in formal letters.
貴姉によろしくお伝えください。
Please give my regards to your older sister.
pronoun
Used primarily by men in letters to address an older woman respectfully. Rare and old-fashioned.
貴姉にはいつもお世話になっております。
I am always indebted to you (older woman).