Born 1894, Buffalo, New York, United States, died 1961.
Worked in Wilfrid Voynich's bookshop and was a long-term companion of Ethel Lilian Voynich, who left her the Voynich Manuscript. Nill eventually sold the document to Hans P Kraus
Two photographs of her can be found here  (along with those of others connected with the VM): other traces can be found on the Ellis Island website and Google Images etc.
More information can be found here  and here , and in other websites on the Voynichs and the manuscript.
Details of her will here .