Coughlin County Clare

[coughlinsearch]

My great grandma Susan Coughlin's marriage certificate states that she was
born in Ennis County Clare to Catholic parents Patrick Coughlin & Mary Murphy- 
We assume she immigrated to Victoria Australia [? direct from Ireland]- maybe 1877-78 as her death certificate in 1905 says she had been in Victoria 28 years.
She was 47 years old when she died so assume she was born around 1857

Cannot find her parents, any siblings nor her shipping record.
Could she have changed her name??? if so, was this common?
Could she actually have been born in another county and moved as a baby???
Would really value any assistance Thankyou