Field, Ellen born about 1841 in County Cork

Hello I am trying to find out any infromation about my Great grandmother Ellen Field, and her ancestry and where she came from. She was born according to the census in Blarney 1901/1911 about 1841, she married John O'Callaghan (RC) in

Blarney on 21st Feb,1871, witnesses,John and Phillip Field. In the register is written Killowen I think,maybe that is where she is from and would love to find out her parents name.She went on to have I think 3 children,Julia, born in Dripsey,then Daniel and John born in Blarney.Also I dont know where John O'Callaghan her husband comes from,born around 1836.I realise O'Callaghan is a very common name in the area, any help greatly appreciated.I now live abroad, so only have online access.