Well, being descended from Earls Rivers did not make her a "princess" as titles such as Earl, being in the gift of the English Sovreign, do not automatically descend indefinitely, let alone make a "Lady" a "Princess". The only title that automatically would convey in this lineage would be that of "Nobilissimus" (for a man) or "Nobilissima" (for a woman) as the Riverses also descend from the several marriages between the Comnenid emperours of Byzantium and (Western) European royalty. In this regard, they could also use heraldically the golden double-headed eagle of Byzantium much as all princes of the Holy Roman Empire could use a BLACK double-headed eagle, as a supporter for their coats of arms. Perhaps in this sense, the Rivers family cntinue to be Byzantine "royalty", and perhaps that was what your mother meant in saying that she was a Princess. A daughter of this Rivers family who really did marry a member of European royalty had her arms altered considerably by her mother-in-law thus: Quarterly of six, 1 not just Lusignan but Antioch-Lusignan with the Cross of Jerusalem impaling Lusignan, 2 de Baux d'Andree with the White star of Balzo quartering France Ancient, 3 Luxembourg, 4 Orsini but ALTERED from what you have here, as "Azure a fess d'or charged with a serpent azure between a rose gules in chief and three bendlets gules in base", 5 St Pol representing Burgundian royal counts, 6 gules the griffin d'or representing the ancient Earls of Devon (Reviers or, Redvers) because the "fess and canton conjoined" of Woodville was used only in her supporters: mermen armoured bearing not only the main escutcheon but, in their free hands, a little shield of Woodville. She also was granted a crest by her royal mother-in-law of the demi-trefoil lad from one of the coats-of-arms used by Anthony Lord Scales. The centre-shields were between quarters 1, 2, 4, and 5 for Myers an altered version of what you have used here: the mullets being replaced by fleurs-de-lises azure, in chief and in base, with the scythes crossed in saltyre and the three black birds in-between, and another centre-shield between quarters 2, 3, 5, and 6 for Christopher which was different from what you have here: rather than the chevron for "Christopher" a canting coat was used for the Dacian Christophori--possibly a different supposed descent than the Fallon kings of Ireland--of a Canting Coat-of-Arms simply showing St Christopher bearing the Christ child across the water. This was for Susie, the late princess who had married into a princely German house.