DANDO, William 39 Amsbury, son of George 16 & Elizabeth 22, bc 1840 Garndaffaith (a.k.a. Garndifath), MON; bap 13.09.1840 Varteg Wesleyan Chapel, MON; m Jane HAWKINS 24.12.1863 Wesleyan Chapel, Pontypool, MON; children: Ada, Elizabeth, Ellen & Emma (both b U.S.A.), William (some slight discrepancy in the names from your list).
In which case the Elizabeth in question, if nee DANDO, would be new to me.William's parents were:
DANDO, George 16, son of Isaac 1 & Hannah 2, b 1816 Frampton Cotterell GLS; m Elizabeth AMSBURY 15.07.1839 St Cadoc’s Parish Church, Trevethin, MON
DANDO, Elizabeth 22 (nee AMSBURY), bc 1823 Trevethin, MON; m George 16 MON