This is a “Betty Karrenbauer” who lived in Darmstadt during the second half of the 1920s.
It could be a Barbara Karrenbauer who was born 21st of January in Püttlingen 1906. This Barbara K lived in Darmstadt in the 1920s, at least until 1932, where she worked as a waitress. Only 18 years old she had a baby, named Erika, out of wedlock.
But it could also be a Barbara who was born Karrenbauer, but change her surname to Daum when she got married, and also lived in Darmstadt during the 1920s. She became a widow in 1944 and worked as a business woman.
And that’s all I know, they don’t have any more information at the Hessisches Staatsarchiv Darmstadt…