If you search birth registrations 1925 + or - 5 years and 1931 + or - 1 year for child DAVIS with mother's maiden name DAVIS in the Westbury on Severn and Monmouth Registration Districts, the two most likely Districts to register the birth, there are none.
Ditto on the chance that she may have been registered as WILLIAMS with mother's maiden name DAVIS.

there are a few possibles ....

Elsie M Davies Oct-Nov-Dec 1920 Westbury S Shropshire

Elsie Davis Jan-Feb-Mar 1921 Westbury S. Shropshire

Gladys M Davis Jan-Feb-Mar 1921 Westbury S. Shropshire

Eunice Davis Oct-Nov-Dec 1922 Westbury S Shropshire

Ruth J Davis Jul-Aug-Sep 1932 Westbury S Shropshire ( probably too late)

Nancy Mdt Davies Oct-Nov-Dec 1922 Westbury S Shropshire

Doris M Davies Apr-May-Jun 1927 Westbury S. Shropshire