Eliza Walsh Irish Famine Orphan

Eliza came to Australia about 1845 aged 14 as an Irish Famine Orphan. She was accompanied by her sister Mary aged 16. Eliza, I think, is my great great grandmother. I am anxious to know where she was born, the names of her parents and where they were born. I have a clue to Westmeath being the county she came from but can't be certain.