I had never heard or read about "Ms." used for divorced women. The proper address for a divorced woman, if a woman kept her ex-husband's name, was, as dirac notes, "Mrs. [First Name] [Married Last Name].
This history of "Ms." as described in this article in The New York Times
is what I'm familiar with:
Moonlily, on 24 September 2012 - 02:11 PM, said:
At least in Germany, 'Fräulein' for unmarried women is nowadays only used very, very rarely. It has a rather antiquated connotation.
I noticed the last time I was there that Fräulein was used rarely, when it was more common in the '70's when I first went. It sounds as antiquated as "Master," the formal address used for a boy.