There is another arrival which may fit - so little information though!
from
New South Wales, Australia, Assisted Immigrant Passenger Lists, 1828-1896
Ellen Collins, 25, dairymaid
Birth Date abt 1816
Arrival: 18 Sep. 1841, New South Wales, Australia
Origin Location Tullogh Co Clare
Vessel Canton
Can Read and Write Neither
Religion Rn. Cathc
Parents: John Collins, Margt
Brought out by Thomas Gore & Co
Under protection of her brother Pat Collins.
This Ellen had a sister, Mary Collins on the same ship, aged 19 all other details the same as Ellen.
You have already noted a marriage for a Mary Collins, registered in Yass in 1842
Volume reference V18421431 92
Mary Collins, John Burnett
Denomination Roman Catholic
With so little information I'm unable to find anything re the brother named as Pat Collins
Judith