Marie Wilhelmine Friederike Elisabeth (von Nassau-Weilburg) zu Wied was the eighth child and fourth daughter of William, Duke of Nassau and wife of Hermann, 4th Prince of Wied. She was the mother of Queen Elisabeth of Romania.
"Maria Wilhelmine Friederike Elisabeth von Nassau zu Wied" Find A Grave memorial (with photos and biography) at this link: 
"Princess Marie of Nassau" Wikipedia at this link: 
"Marie Prinzessin von Nassau-Weilburg" at Peerage.com. See this link: