There is a William Wyatt whose birth is registered in the Tiverton district in the March quarter of 1848 with no maiden surname recorded for the mother. I have been unable to find a baptism for this child You can download a digital copy at the birth entry GRO website for £3, presumably he is Elizabeth's son and not that of her future husband. There are very few surviving census records from before 1841.I think further records of Elizabeth are in Bristol and not in Devon