Margaret Kerr (Mcgory) - Margaret Kerr

From my research Margaret Kerr nee McGrory Departed London 2 Sept 1863 on the Echunga - arrived In Lyttelton 24 December 1862.
According to the vessels Passenger List
Margaret was 42 years old and accompanied by Daughter Agnes 19, and sons John 11 and James 9 years old.
Henry Kerr arrived in Lyttelton 14 December 1861 on the Sebastopol.
According to the Passenger list
Henry Kerr was 40 years old and accompanied by 2 Sons Edward 16 and Henry 17.

Then all the rest of my information came from the Publications By Christine Clements "Pioneers Settlers and Families of Te Puke and District"
it was in this publication Margaret Kerr maiden name is stated as McGrory
I cannot find any reference to Margaret Kerr nee Rogers. Can some one explain the relevance of Margaret Rogers.
Margaret is my Great Great Grand mother - Emma Jane married my grandfather.
Earl O'Callaghan