Would you clarify something? Is the wireless router hooked directly to a cable or DSL modem and is simply sitting next to your wife's PC? That would be the more common configuration.
Assuming that's the case, you can continue connecting additional devices (such as the Squeezebox Touch or another laptop) wirelessly to the router. The Touch could then stream music from your iMac. Note you'd need to install the Squeezeboxserver program on the iMac to provide the stream.
Assuming that's the case, you can continue connecting additional devices (such as the Squeezebox Touch or another laptop) wirelessly to the router. The Touch could then stream music from your iMac. Note you'd need to install the Squeezeboxserver program on the iMac to provide the stream.