LOL Christophorus Columbus
Regina Isabella.
In Spain , actually, she is named Isabel la Católica
but if you want to be more precise, know that she signed Ysabel and in portraits and coins Isabella, for latin was then diplomatic, liturgic language. Isabel la Católica spoke and wrote latin perfectly, so that she referred often to herself as Isabella. Isabel didn't exist in XV century. Historians of other traditions and countries have employed other names : Elizabeth, Isabela, Elizavetha, Erzebet,Isabelle, Ysabeau, Lisbeth, Sabela, Lisette, Lilie,Liz
. All valids, why not? She, however, i repeat, signed Ysabel, pronounced /i s a b E l / Her spanish subjects referred to their queen like this. Whe she spoke wrote letters or documents to pontifical or extranger courts she wrote in latin . An island in america was called "The Isabella" in her honour in fact. Both forms were used in both registers: cult and popular, latin anbd romance.
I think the logical form here wold be Elizabeth queen of spain for we are writing in english. If you prefer Isabella Regina Hispaniorum Regnum, OK, but you must go on in latin
