I joined FindMyPast today and found Elizabeth, daughter of Nicolas and Elizabeth Tresaddern, baptized 13 Aug 1751 in Perranarworthal. Since they are so close, I think this is the same person. Although I took notes on Elizabeth before I realized I needed to document where I got my information, I believe the Kea location came from the marriage record, which is the only document I had about her. Like you, however, I am still very intrigued by the Thomasin. With the similar last name and location, I am pretty certain they must be related, especially when they chose to share a wedding date. Also, a Nicolas Tersadren was baptized on 29 Oct 1727 to John! Thank you for your help. This will definitely be something to work on.
David