I have come accross Catharin's Cornelisz Baptism records, and it states her father was Evertsz Cornelisz and mother Maria (dogter syn genamnt, Catharin.) Date of baptism 2 July 1673.
Uploaded it under her Media.
The Syn Siegertz I thought was a surname, is actually... Dogter syn genamnt - daughter named) Catharin.