Here is the registered birth index entry for the last member of Revd John Dumbell & Ellen's family:

Name: DUMBELL, Mary Hannah
Registration District: Oldham
County: Lancashire
Year of Registration: 1861
Quarter of Registration: Jul-Aug-Sep
Volume No: 8d
Page No: 511

Perhaps Marion was a pet name for her. In official records she seems to be Mary Hannah.

NZ deaths:
Registration Number Family Name Given Name(s) Date of Birth/Age at Death
1945/26881 Triggs Mary Hannah 85Y

NZ marriage:
Registration Number Bride's Given Name(s) Bride's FamilyName Groom's GivenName(s) Groom's Family Name:
1882/669 Mary Hannah Dumbell William Henry Triggs

Sue