Merged (don't worry, it was probably just a server hiccup).
I can at least provide you with the French birth of daughter Rosa Clara Giselle Vetter which gives her mother's maiden name.
http://archives.marne.fr/?id=recherche_guidee_etat_civil(she was born Reims 16 Dec 1880 and registered on the 17th)
This link may work (she is on image 342, bottom left)
http://archives.marne.fr/ark:/86869/a011310543791b86W1p/1/1Registered by midwife, Marie Claire Farce, aged 26, mother Rosa Steinecker, 25, gymnast, wife of Frederic Guillaume Oscar Vetter, 25, gymnast, residing in Berlin.
"Rue de la Peiriere No 5" was the place of birth, the residence of the midwife, and also the address of the witnesses - Jean Baptiste Rouge (40) and Adophe Melingue (43), occupation of both listed as artiste lyrique - opera singers.