Societal changes to the use of "Mrs."
Tradition held that a married woman should use the title Mrs. only in conjunction with her husband's name, not her own--"Mrs. Arthur Reynolds" rather than "Mrs. Susan Reynolds." The latter was acceptable only in the event of divorce. But societal changes gradually made this practice seem a relic from another time. Today it is acceptable for both married and divorced women to be referred to by their first names after the title Mrs.--as in "Mrs. Mary McGowan."
A married woman can choose to be addressed as either "Mrs. Mary McGowan" or "Mrs. John McGowan." In the case of a divorce woman, Mrs. [or Ms.] is correct only if she has retained her former husband's last name and she uses her first name, not his. (Many women retain their married name so that the surname won't differ from their children's.) Otherwise, she is referred to as Ms. or Miss.