Dorothy Loftus and Sir John Moore, of Offaly/Kings Co.

Hello, Cindy. That was back in the mists of time! 

Are you certain of Dorothy's birth year?*

According to a tree on Family Search Dorothy's father was Reverend Adam Loftus. 

Rev. Adam Loftus has a page in Wikipedia. He was born in Yorkshire and his father worked for the Catholic Church. Then the Reformation happened. Adam changed his religious allegiance depending on who was on the throne and which faction was in power. He was ordained as a Catholic priest and came to the notice of Queen Mary, who was Catholic. Queen Mary was suceeded by her sister, Elizabeth who was Church of England, so Adam became an Anglican clergyman. He went to Ireland at a tumultuous time. He became Archbishop of Armagh and later Archbishop of Dublin. He was the first Provost of Trinity College, Dublin. He also served as Lord Chancellor of Ireland from 1581. He had the Bishop of Cashel tortured and executed.

Archbishop Loftus had Rathfarnham Castle built, and lived there from 1585.

Adam Loftus and Jane, his wife, had around 20 children. A lot of them lived long enough to marry. Dorothy's baptism and her marriage would have been Church of Ireland.

* The reason I asked about Dorothy's year of birth is that if it was around 1597, Adam's wife, Jane would have been too old to have been her mother. Adam and Jane were said to have married, quietly about 1560. (Wikipedia) Jane's approximate year of birth is given as 1540. If both Dorothy's and Jane's birth years are correct, Jane might have been in her late 50s when Dorothy was born. According to Family Search, there were more children after Dorothy. 

As Adam Loftus was from Yorkshire, the origin of his surname is likely to have been Lofthouse. Loftus in the west of Ireland is of Gaelic origin. Mine is the Gaelic Loftus from Mayo, so no connection to the family of Adam Loftus.

A Dorothy Loftus who was alive around the same time is in several trees on Ancestry but many of them are suspect. Birth years vary by 2 decades.

P.S. Have you explored wills and marriage settlements? Also land and property records.