From the Bain collection of the USA Library of Congress; spots and other flaws removed with Photoshop and the image was reposted on 17 October 2016. Wikipedia has a similar photo and dates it to 1910.
This photo of Princess Eitel-Fritz shows the sort of trim that could be used on a neckline.
Keywords: 1910, Sophia Charlotte of Oldenburg, Sophie Charlotte von Oldenburg, Prinzessin Eitel Friedrich, Princess Eitel-Fritz, Princess, Oldenburg family, Hohenzollern family, German, bouffant coiffure, necklace, vee neckline, modesty piece, bertha, floral bodice ornament