I think the reason this must have been discounted in the past, is the ages given on the census and wedding - all are out, gives 5 years younger at her wedding and 9 years in the 1901.
I shall check the census at the archives as its only the transcriptions I have. Still to locate death I am sure its May as you say. Without the 1855 certificate to corroborate the facts it was easy to have added an extra child!