She's fictitious. People used to have pedigrees done on ornate scrolls with names in roundels. They didn't want to have blank roundels, so if they'd forgotten a wife's name or added on some extra generations, they would make up names.
Usually they'd invent an heiress to explain every property they owned and/or every quartering in their coat of arms. Maud Gawkthorpe was made up to explain the Gascoignes' possession of Gawthorpe. But they didn't get it from an heiress.