CP states she was the heir of her father. Test Vet says, p. 446, this has to be rubbish - unless there were two brothers John.  DNB says there were, indeed, two brothers John.  Anyhow one of the brothers John had a son Edmund who was his heir.
To be sorted?  Hopefully.
The Surrey Visitations of 1530-1628, p. 50, shows two John Brays, of whom Margery's father was the elder.