Thought it might help if we could find out where and when she was born, and there is this possible baptism for her:
https://www.ancestry.co.uk/interacti...73438626/facts
St Leonard, Shoreditch, 13 May 1781
Rebecca D of Thomas & Jane Newman of Norton Follgate, born April the 3rd.
Thomas Newman married Jane Fray 8 Apr 1776 at St Mary Islington which is why I think this could be her. There is a public tree which shows Jane Fray's father as a John Fray b 1717 and also shows Jane having a brother John Fray born 1753. So John Fray Miller could have been named after either of them, and the marriage witness could have been the one born 1753.