Lady

The term Lady is used as an honorific for woman to indicate that they or their close relative has rank. In modern England, a wife is called a Lady if she is a marchioness, countess, viscountess, baroness or baronetess, if their husband is a knight, baron or baronet or if their father is a duke, marquis or earl. It can also be used for the wife of the younger son of a marquis or earl.

Hence, you could introduce the Baroness of Outerkeep, Lady Catherine.

a Lady of the SCA

In the SCA, it is the title given to a woman who has been given an Award of Arms. It is also commonplace to refer to any woman at an SCA event as "my lady" but that implies no rank.