For information and possible elimination the following address:-
www.connfamily.ms11.net/95.html#i2030references Catherine Bridget Foulkes with Australian connections and despite slightly awry chronology at one point claims
born to Thomas Foulkes and Sarah Denbighshire 1835
other siblings
John born 1831
Anne born 1833
Edward born 1837
Thomas born 1840
There is such a family on the 1841 census in Henllan
HO 107 1402 4/47
with Thomas given as b.1806(gamekeeper),Sarah b.1801(see later)
Between Family Search.org and the Blackwell Index(which at times has her transcribed as Sinah) the data looks consistent
There is a mariage recorded in FamilySearch.org("Sinah")which looks appropriate
Thomas Foulkes/Sinah Conway 12th Dec 1829 Henllan
The only inconsistency is a possible birth for SarahConway.The nearest which would still have her as 18 at marriage is
Sarah Conway 1811 Denbigh parents George and Ann
Roger