Her two younger sisters having been made nuns in the Priory of Aconbury, not necessarily willingly, Joan became sole heir of her parents to all their estates in England and Ireland. Nothing to do with her husband of course.
She received a papal indult for full remission of her sins in 1346.
As with other members of the Mortimer family, it is believed she was buried at Wigmore Abbey in Wigmore, Herefordshire.
Weis, Frederick Lewis, Ancestral Roots of Certain American Colonists who Came to America Before 1700, 7th ed., Baltimore MD: Genealogical Publishing Co., Inc., 1992. Access online (search only) at GoogleBooks, Line 120, p.107.
Douglas Richardson, Royal Ancestry: A Study in Colonial and Medieval Families, 5 vols., ed. Kimball G. Everingham (Salt Lake City, Utah: the author, 2013), Volume IV, pages 170-172 MORTIMER #10. Roger de Mortimer, Knt., #10.v. Katherine de Mortimer.
Douglas Richardson, Royal Ancestry: A Study in Colonial and Medieval Families, 5 vols., ed. Kimball G. Everingham (Salt Lake City, Utah: the author, 2013), Volume III, page 680.