I am really interested in princess Anna of Prussia, daughter of prince Karl and his wife Marie of Saxe-Weimar-Eisenach. She was the second wife of Wilhelm of Hesse-Kassel and bore him 5 children (Friedrich-Wilhelm, Elisabeth, Alexander, Friedrich-Karl - Mossy's husband - and Sibylle).
Young Kaiser Franz-Josef met her in Berlin in 1852 and was quite taken with her. He actually wished to propose to her but she was already engaged and, besides, Prussia was opposed to a union with Austria.
That is about all I know - very little indeed - and would welcome any info on her as well as pictures (I have seen her portrait by Winterhalter). Cheers.