1) Does she want to have different rooms to be able to play different music at the same time?
2) Do all of the audio sources come from the same PHYSICAL location? If she wants to put the ipod the living room but listen to it in the kitchen, that becomes more complicated.
I would suggest several audio distribution amplifiers (DA) to provide an isolated line level audio signal to each room. In each room, have a small wall box that contains a selector switch and volume control. The output of the volume control would then run back to the central location that has a dedicated amplifier for each speaker or room. This way, any room can select a music source without affecting anybody's elses music.
This is the same sort of idea you see on airplanes. Everybody can select what they want to listen to, the volume for each room can be limited to a maximum level at the amplifier, and if you want to provide some sort of overide for alarms or PA applications, that can be implemented at a later date.
