Not sure if this is good news or bad news for you Mike. I actually have that 1878 death certificate. Mainly because of the appearance of the name Ellen Donohue which ties to my Jackman/Chapman line.
Details: 18 april 1878, Green Street, Wexford; Patrick Jackman, married, 50 years, carpenter, Pneumonia with Diarrhoea 6 days, certified, Ellen Donohoe present at death, Patrick Square.
However I also have this cert:
Details: 12 oct 1878, Newtown, Margaret Jackman, married, 57 years, carpenter's wife, Bronchitis 2 months, certified, Ellen Donohoe present at death, Allen Street, Wexford.
Were they husband and wife? Well, Margaret is a similar age, but not noted as a widow. The occupation is suggestive. Her different address (of the dead people, not witness) might reflect a number of situations. The same person registering the deaths does seem to tie them together though. But her name is not Anne.