i Register
In some senses, mistressship is marked as obsolete. Watch for register when choosing this word.
noun
Female rule or dominion.
ladyship; a style of address, used with the personal pronoun.
Your father was / An honest country farmer, goodman Humble. / By his neighbours ne'er call'd Master. Did your pride / Descend from him? but let that pass: your fortune, / Or rather your hunsband's industry, advanced you / To the rank of a merchant's wife. He made a knight, / And your sweet mistress-ship ladyfied,