parish records won't show on FreeBmd, only civil registrations.
Have you asked the local registrars to check for the birth registration? Email
registrar
atbridgend.gov.uk replacing
at with @
It's possible that her birth wasn't registered. At this time, the onus was on the registrar to record the births, not the parents to register. Fees for non-registration didn't come in until the mid 1870s.
If you want the birth cert to confirm mother's maiden name, you could get one for one of the other children.
David Whitney march qtr 1845 Bridgend vol 26 pg 366
Mary Whitney march qtr 1847 Bridgend vol 26 pg 364
Hannah Whitney march qtr 1849 Bridgend vol 26 pg 259
It looks likely that the marriage reg is
Thomas Witney & Mary Anne Collier june qtr 1842 Bridgend vol 26 pg 541
1851 sees them living next to some Colliers.
