This is not the Agnes Fawcett who married a George Mason in 1648 at Dent! According to Paula Healey, that George Mason was Thomas's brother (29 Dec 1616-), and he had at least 2 children: Miles b1649 (son of George son of Miles deceased in 1618); Mellory b1652 (daughter George brother of Anthony of Dalehead 1618-1684).
not sure when this Agnes was born. father John Fawcett of Winterscales, Lower Garsdale in 1661, Agnes is mentioned in her father's will, she was still unmarrried at the time
m about 1665 to George Mason of Borronhead, Dent (just above Cowgill) (54.2803 -2379) d 3 Jan 1675 at Dent, FHL 1472792/2 #232
in 1683, Agnes is mentioned in her mother's will: Agnes Fawcett Unknown (-1683)