Which preposition to use with mistris

of Occurrences 4%

Dost thou heare, [Sidenote: fauning;] Since my deere Soule was Mistris of my choyse; [Sidenote: her choice,] And could of men distinguish, her election Hath seal'd thee for her selfe.

to Occurrences 1%

Celia alias E[n]anthe, Daughter to Seleucus, Mistris to Demetrius.

Which preposition to use with  mistris