Lucy Sheffield was born about 1360 at Woodhouse, Yorkshire, England.[1]
(14) Thomas Wentworth, Esq., who married Isabel, daughter of Sir William Fleming, Kt., of Waith, in Lincolnshire, and had issue: -- [2]
(15) William Wentworth, Esq., who married Lucy, daughter (by a former husband whose name is not preserved) of Isabel, wife of William Sheffield, Esq., of Bolderstown, and had issue:-- [3]
(16) William Wentworth, Esq., who married, first, Isabella, daughter of Thomas Durrant, Esq.: and, secondly, Isabel, daughter of Sir Thomas Reresby, of Thriberg, in Yorkshire; and by the former had issue:-- [4]
From the excerpt above it appears that William Sheffield is Lucy's step father and that the first husband of Isabella is not known.
The Isabella currently linked to Lucy is not likely to be correct. as the only St Elizabeth I found was Portuguese from a hundred years earlier.