Traditionally, Mr. and Mrs. are used after a couple gets married.
She still is a Mrs. The women I know who have kept their names use the Mrs. with their own name. So, if she is Kate Smith and marries she becomes Mrs. Kate Smith.
By their first names, if it's informal. Otherwise Dear Mr ...... and Mrs/Miss/Ms .........
Miss has no punctuation, Mrs. has a period at the end
ask mrs amerson
Mrs
Ms. is pronounced "Miss" and Mrs. is pronounced "Misses". You pronounce "Ms" as "Miz" and pronounce "Mrs" as "Miss-es"
She is a Mrs.
mr ans miss or.... for mrs is madame. mr ans miss or.... for mrs is madame.
Mrs= married lady Ms and Miss= non-married lady
mademoiselle=miss madame=mrs
Since only few places in America recognize same sex marriage, Thee appropriate title for a cupple of the same sex (in this case Lesbians) is a domestic partnership. They would still be called Mrs. And Mrs. But that is do to gender not Marriage.