Why is her Name Sometimes Spelled "Therese", "Theresa", and "Thérèse"?

All three are appropriate, but if one is to remain faithful to her actual French name, it is "Thérèse". In English, we don't have the vowel marks which the French have, so she is simply "Therese". It became popular to use the more Anglicized version "Theresa", but more recently it has caused confusion between her and Teresa of Avila. In order to avoid confusion between the two Carmelites, many choose to use the spelling more reflective of her French name, "Thérèse". We believe she answers to all of them.