Burke in 1853, Ricketts article, p. 1118, says that this lady was the daughter of Sir Thomas Wiseman who "derived from Anne, sister of Edward IV, through the noble families of Rutland and Essex".  I cannot find anything that makes sense of this in Ruvigny's Exeter volumne; there was a Sir Thomas Wiseman in the descent but he lived too late.  In the 1871 edition this paragraph is omitted.