Based on all that, I think she was probably the daughter of a French ambassador to Austria, and that she stayed on there after her father's post ended. I suspect her relationship with "serious" Frederique was similar to what she had with Harold, that she wanted to save him from his own darkness and teach him to love life, however, in this case, she failed. While she demonstrated against rise of fascism, he joined the fascists, possible even the Nazi Party following the annexation. At the risk of writing melodramatic fan fiction, he may have even turned her into the authorities himself.