Could this be her? From FreeREG:
St Mary the Less Westley Waterless . Other Transcript . Cambridgeshire
Baptism: 31 Mar 1870 . Isabella Alice Webb
Mother: Selina Ann Webb . Singlewoman of this parish
I cannot find a marriage, though they may not have formally married.
Added:
Isabella Alice Webb . mmn /
Apr-Jun 1870 . Newmarket . Volume 03b . Page 541
If her, this is her mother's baptism and parents.
St Mary the Less Westley Waterless . Other Transcript . Cambridgeshire
Baptism: 06 Sep 1846 . Selian Anne
Father: William Webb . Labourer . Mother: Mary of this parish
With fixed locations, she does not seem a traveller, though she could have married a traveller.