It looks as if Mary Ann maybe the illegitimate daughter or Harriet
Mary Ann Prior Hemmings
Baptism 2 Jun 1867 Tackley, Oxfordshire
Mother: Harriet Hemmings
HEMMINGS, MARY ANN -
GRO Reference: 1867 J Quarter in WOODSTOCK Volume 03A Page 652
Harriet Hemmings f/a father Joseph,labourer
married on 26 Dec 1870 Bladon, Oxfordshire
Spouse: James Prior f/a, labourer father John, butcher