John Benson the Convict

John Benson was transported to Australia in 1833. He later married a Margaret Walsh from Ireland. I would love to know if she had been a convict too. There were a number of convicts with her name transported out here. If she was not a convict - what made a young girl leave Ireland by herself. Was it because of the famine or what?
Would love to find out more about her and also about John's family.
John settled in the Macleay River Area - Kempsey region of Australia.
I also collect old photos of the Benson, Minter, Batterson families.