"Illogan is an Ancient Parish in the county of Cornwall.Other places in the parish include: Brea, Bridge, Carn Brea, FOREST, Illogan Downs, Pool, Portreath, Trevenson Moor, and Voguebeloth. Illogan (Cornish: Egloshal)is situated in the Deanery and Hundred of Penwith"
The IGI (familysearch) doesn't cover the year she was born, nor does the Cornwall OPC site, so that explains why her birth is not in either of those sites.
If she was born in Forest, then the baptism record might appear eventually because people with earlier birthdates are on the Cornwall OPC.