No Problem Sally- I have solved the riddle!
Mary and George's children were not on Freereg, but I found them amongst the non-conformist records, so I went there looking for Mary Richardson.
I found 2 children born to Mary and Aaron richardson in Norfolk- Robert Pursglove born 1779 and Rachel Isabel born 1780. Robert the son and Aaron both died in Norfolk in 1780.
So based on the witness of the marriage to George Hawkins- Rachel Pursglove, I took the chance this was the right girl.
Found a will on NOAH for Robert Pursglove in 1813- turns out he was Mary's brother, and his will confirms she was Mrs Richardson, and then became wife of George Hawkins.
So the riddle is solved in so far as I have her true identiy now.
Just have to find her marriage to Aaron Richardson pre 1779 now!
Many thanks
Kylie