Answer to Carmelita: The host has admitted her mistake and returned our money. Just FEWO-direkt and HomeAway are sitting on what´s obviously their share of the loot and wont admit their error and return our money. Unfortunately they have the nasty habit of sending you only "NO Reply" emails, so you can´t really communicate with them.
Use only AirBnB if you want to be sure not to be cheated by that bunch of crooks at FEWO and HomeAway.