Quite a lot of children blanked out at 17 David Street on the 1839 census, so one could be Gladys.
Not certain, but there is a marriage of Annie Williams, in Conway District Jan-Mar 1924, to Shadrach Davies, and a death of Shadrach Davies in Jul-Sep 1931, born c1881.
In 1911, there was a Sadrach Davies, born Caernarfon in 1882, boarding at Celyn Villa Penmaenmawr, Dwygyfylchi, Caernarvonshire.
In 1921, he was still at Celyn Villa, transcribed as Sadiack, brother of Edward Davies, whom was born in 1876.
The marriage article states that Edward Davies, of Celyn Villa, was the uncle of Gladys and gave her away.
In 1901 Shadrach was also with his brother at Hwynfryn Cottage, Paradise Crescent, Dwygyfylchi, Conway, Caernarvonshire.
David