James Moore and Mary C. Moore, siblings born in Thurlas

Hello,

I am seeking information about my great-great grandmother Mary C. Moore, born abt 1845 in Ireland, arriving in New Orleans abt 1856 (according to 1900 US census) with her brother James.  I have found a passenger manifest for the ship Ellen arriving New Orleans 15 Mar 1857 from Liverpool listing James Moore (age 15) and Mary Moore (age 12) but have no way of knowing if that's the Mary Moore I'm looking for. 

Mary C, Moore's New Orleans death certificate states she was a daughter of Robert Moore and Nellie Carroll of Ireland.  We have not found any evidence that the parents immigrated with James and Mary C. Moore.

I have one possibility about Mary C. Moore's birthplace:  when her brother James Moore died In New Orleans December 1907, his short obituary stated he was born in Thurlas, Co. Tipperary, as does his headstone which also adds a birth date of August 1839. His death certificate does not list his parents but does identify Ireland as his birthplace.  Perhaps his sister Mary C. Moore was also born in Thurlas or at least in Co.Tipperary.  Both Mary and James were Catholic.

Several Robert Moore's are listed in Thurlas in Griffith's Valuation, but we have not been able to identify if any of them as the father of James and Mary C. Moore.  We've never even seen Mary's middle name written out so unsure what the "C" stands for - could it be her mother's maiden name Carroll?

Mary C. Moore married Dennis Manning of New Orleans in 1867.  They had four children before Dennis died in 1880.

Any clues/advice about the missing puzzle pieces in Mary C. Moore's life or about her parents Robert Moore and Nellie Carroll would be appreciated.

Thank you.

Sheryl V.