Ancestry has a number of on trees featuring her saying that she was born 1788, in Pembrokeshire, and that here parents were John Rixon (1760-1808) and Elizabeth Morgan. These trees cite the Bishop’s transcripts for Pwllcrochan, as evidence of her baptism. Unfortunately a copy of the original of that document is not attached to enable independent verification. What at least one of these tree has are fairly well documented citations, to take the tree back a further two generations:
John was the some of Stephen Rixon (1731-1798) and Mary Enion. Stephen being baptised at Pwllcrochan. His father was William.
That tree also says that the surname can be spelt Rickson, or Riskston.