Stop press, I'm on a different trail now.
Is she the one who gives Rosemarket as her birthplace on later census returns?
If so, I can see this in
1861Haverfordwest Rosemarket (Registration district Pembroke)
RG9/4159 80 8W Gwynne, head, 33, Labourer, b. Pembrokeshire St IshmaelsMary, wife, 36, b. Rosemarket
Henry, son, 5, scholar, b. do.
Martha, dau, 2, b. do. I agree this is not much help as far as her birth is concerned