Hi there
I have looked at my Visitations CD, and the TREMAYNE's and Sithney PENROSE's seem to have linked around this time through Elizabeth and Laurence, and Jeffrey PENROSE AND Mawde TREMAYNE.
Elizabeth is not mentioned on the Visitations - very few women were mentioned in the family trees from about the 15th century backwards in time that were not heirs.
From the date, I believe her to have been either a cousin or sister of Jeffrey's.
Without further sources such as wills and deeds, and the original parish registers, I couldn't say anything for sure.
Regards
Chris