This vintage real photo postcard features French stage actress Mlle. Ziska. Preliminary research found little information about this actress. There are a few postcard views of Mlle. Ziska that can be seen online. One of the cards is a photograph of her appearing in “Salome”. However, I could not find her first name or any other biographical information.This postcard close-up portrait of Miss Ziska highlights her beauty. The photograph was taken by Walery. He was a well known and talented celebrity photographer who operated out of Paris, France. The postcard is hand colored. The card was published by SIP as part of a series (no.5096). (SOLD)
THE CABINET CARD GALLERY 
I think your are looking for Ruth St.Denis.
https://en.wikipedia.org/wiki/Ruth_St._Denis
At some point in her travels of Europe she incountered Mary Mackay. Better know as Marie Corelli, author of Ziska
https://en.wikipedia.org/wiki/Marie_Corelli
In one photo, cover for her book was Ruth St.Denis.
https://www.loyalbooks.com/book/Ziska-by-Marie-Corelli
And this……
https://www.storytel.com/tv/books/ziska-2089731
which brough me to this….
https://www.ebay.com/itm/293813214046
That was fun 😂
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Thanks for sharing your extensive research about this postcard. I would not have imagined that “Ziska” was a novel and not a person. It appears that you did some amazing detective work.