Jenny Wiegmann was born in Berlin-Spandau. Her parents supported her artistic talent when she was still young. In 1917, Wiegmann entered the Levin-Funke School in Berlin, where she studied with August Kraus and Lovis Corinth. She also studied sculpture there. In 1918, she continued her studies in Munich before moving to the School of Applied Arts in Berlin-Charlottenburg, where she joined the woodcarving class of Hans Perathoner. She took part in the 1928 exhibition of the Berlin Secession, in the 1929 exhibition of the association Die Juryfreien, and in the annual exhibitions of the Prussian Academy of Arts. After separating from Muller in 1930, she moved to Paris to be with Gabriele Mucchi, whom she married in 1933. In 1934, they both moved to Milan, where Wiegmann-Mucchi became known under the pseudonym “Genni”.
After 1932, Wiegmann-Mucchi no longer took part in German exhibitions, though she exhibited in Italy from 1934 onwards, and one of her bronzes was shown in the Italian pavilion at the International Exposition in Paris in 1937. The Mucchis’ home became a meeting place for artists and intellectuals in Milan. In the late 1930s, the prospect of war became ever more real, even in Italy. In 1943, their house and studio were destroyed in a bombing raid on Milan, along with many of their works. Wiegmann-Mucchi joined the Italian resistance against the fascists, and fought with the partisans until 1945. She smuggled weapons, documents and information for the Communist Party, travelling on her bicycle. After the end of the war, Wiegmann-Mucchi joined the Realismo artists’ group and was appointed a lecturer in metalworking at the Scuola Umanitaria in Milan.