"Happy anniversary Sister" is an English expression used to convey warm and joyful congratulations to one's sister on the occasion of her wedding anniversary. It serves as a way to celebrate and recognize the enduring love and commitment between a sister and her spouse as they commemorate another year of their marriage. This message typically conveys well-wishes, love, and happiness for the sister and her partner as they mark their continuing journey together. It's a thoughtful and affectionate way to express appreciation for the special bond shared with a sibling on this significant day.

A sister is a person born into the family before or after you. She is a friend and confidant.
Surely your best sister lovingly saves all the messages you exchange and she will like to keep this detail too. Show her how much you love her and how much you value her friendship.