The suggestions I gave of “Ms./Mrs.” and “Doctor” are perfectly polite for a Protestant clergywoman.
Keep in mind that I was careful to state “Insofar as Catholics use priestly titles such as ‘Father’ and ‘Bishop’ for Protestant clergy, they are used solely as a courtesy…” (emphasis added). Catholics should not use titles for non-Catholic clergy that are likely to cause scandal. Given Catholic belief in the reservation of holy orders to men and the current confusion that reigns on that issue, it could cause scandal for Catholics to use the priestly titles Anglican “priestesses” usually prefer, which are “Mother” for a “priestess” and “Bishop” for a “female bishop.”
While I agree that Catholics should be polite whenever possible – which is why I stated that titles expected by non-Catholic clergy usually are used by Catholics as a courtesy – Catholics must also remain true to their own beliefs. Any Protestant clergywoman who bristles over an honorific such as “Ms./Mrs.” or “Doctor” rather than “Mother” or “Bishop” should gently be reminded that many Protestants also refuse to call Catholic priests “Father” out of conscientious objection.