From the info you've given, it's possible that Mary Ann didn't know her mother's maiden name although without knowing how it is actually written on the MC its difficult to say.
Although, this is the Mary Ann you are claiming. Her parents are John DYKES and Mary DYKES!
Vic Birth.
DYKES
Mary Ann
Mother: DYKES, Mary
Father: DYKES, John
BELFAST
1858
12959/1858
bitzar.
