With sister Wilhelmine (1861-1948) and brother Christian (1862–1924), she grew up in Rotterdam, and, after her parents' divorce on 15 November 1869, in Berlin, where she learned German.

[2] In 1878 at the age of fifteen, Sandrock made her debut as Selma in Mutter und Sohn by Charlotte Birch-Pfeiffer.

Burgtheater star Charlotte Wolter was her great supporter and even borrowed her a fur coat for her costume.

She provoked disagreement concerning both her contract and her private life, and left for an extended European tour in 1898.

In 1905, she moved back to Berlin, to work at the Deutsches Theater led by Max Reinhardt.