Wife of Rowland Hughes died in 1849 ( Mary Hughes. She is buried at Belmont. Belmont I assume is in Wisconsin. I am not sure. Unfortunately it does not mention when nor where she was born. Only detail by her name is widower Rowland Hughes. from Anglesey.
Details came from Anglesey 1838/1849 Book on Emigrants from Anglesey Wales to the USA.1795-1932.
The details I sent you before are the same family as they are living at MORFA, Llangristiolus.the same place as your list of Richard Hughes etc.
There is no grave at Llangristiolus for Richard & Margaret Hughes, but maybe they were buried at Cerrigceinwen, the neighbouring church.