I caution against trying to over-interpret the term in the light of modern usage.
It may signify nothing more than the fact that she has been married previously. She is Mistress M(?)eisstin because she is no longer Miss McPherson but nor is she still Mrs Meisstin.
One might have expected the same courtesy to be offered to the divorcee on the facing page, but note that the two records were created by different Deputy Clerks. I suggest you step through some more images in the set to see how other "previously married" ladies are described.