I can think of two bipeds - the trait is very rare - birds and humans. The first known bird ancestor, Asilisaurus kongwe, appeared about 245 million years ago so birds have had a long, long time to get bipedalism down cold (assuming birds are extant members of the therapod group of dinosaurs made notorious by Velociraptor). We're not so lucky. Shifting from tetrapod locomotion for humans, shown here, occurs between the ages of about 9 to 18 months. Cecilie's first son, Wilhelm, was born on 4 July 1906, so this photo could date to later 1907 which is about when her second son arrived. This may explain the fullness of her bodice?
The card was identified on eBay as being by Adele, but Atelier Adele (Adele Perlmutter-Heilperin and her two brothers, Max and William Perlmutter) apparently closed in 1905, before Cecilie bore any children. Sepia tone removed by gogm.