There is no Birth registration for Mary Mather. Maybe she is Mary Butterworth (MMN = CRABRETT), adopted into this family.
There is a birth registered for Mary Mather (MMN = RYDER) with no apparant 1841 census record. This could be her.
In 1851, 1861, 1871, Mary (aged 12,22,32) is with her parents James and Sarah
27 Oct 1889, Mary Mather, daughter of James Mather married William Wolstenholme son of William at Birtle, Lancashire, England
In 1891, William a farmer and Mary (38 & 42) were in Birtle with Mary's mother Sarah Mather (76)