Thank you for the look-up in the passenger records in the State Library of South Australia.
I have looked in a copy of the South Australian Register of November 27th 1855. According to the Register the name of John Mullan's wife is "Rosanna".
"Monday, November 26 - The ship Glentanner, 610 tons, Benjamin Bruce, master, from Plymouth August 23. Passenger- Dr. S. Hughes, Surgeon, Superintendent, In the cabin, Goverment emigrants- John and Margaret Brown, Michael and Judy Cormick, Adam, Margaret, Mary and Lawrence Coleman, ... John and Rosanna Mullan..... Mary Spain.... and many other passengers too."
As their is no death registration in South Australia for Rosanna Mullan, she may have died already abroad the ship while coming out from Plymouth to Port Adelaide (during the vovage).
Another possibility what I have to check is that perhaps the Catholic Church Archives in Adelaide have listed Rosanna Mullan in the burial register.
Would you perhaps know if the passenger records have details of the people who died abroad the ship?
I would be thankful if you could perhaps check the passenger records for a possible death of Rosanna Mullan abroad in the Glentanner in 1855.
Thank you very much for your fantastic assistance with my research. Your help is extremly appreciated. Many thanks, X Mullen
As the story was told in the family that John Mullen and Maria Spain met abroad the ship while coming out from Plymouth to Port Adelaide.