This Jane Seys is on my husband's family tree - she was his GG aunt and was a daughter of William Seys and Mary Ann Wells. She married Thomas Sheppard in 1874 in Chepstow and they had 2 children, James b 1874 and Kate b 1877. They lived in Woodcroft, Tidenham in 1881, her father living with them. He died 1884 at 7, Newcomen Rd, Battersea aged 97 while living with Jane & Thomas. He was a fisherman and quarryman.
I don't know when she died. SAIS is the original spelling of SEYS and is from the Welsh meaning 'stranger' or 'Englishman'. The last SAIS birth I have found was in 1980.