I couldn't find Sarah in the 1841 census, but did find her on FamilySearch in the 1861 Census and 1881 Census.
I also found a baptism record for Rebecca on Findmypast:
Record set Essex Baptism Index 1538-1920
First name(s) Rebecca
Last name Pullen
Baptism year 1849
County Essex
Country England
Place Romford, St Edward the Confessor
Mother's first name(s) Sarah
Father's first name(s) John
Father's last name Pullen
Baptism date 29 Dec 1849
Father's occupation Stone Mason
Residence Romford
Archive Essex Record Office
Archive reference D/P 346/1/6