The way mine works (might depend on firmware version), you first connect to your wife for the intercom (short press on the button/wheel). Then, once connected, you start the music playing (long press on the button/wheel until you hear the beep). She will now hear the music that you hear, however, you wil no longer be able to communicate via intercom. That seems to be the drawback to Sena's implementation...either intercom or shared music, but not both. However, it's better than it was before where you either listened to your music (alone) or you talked on the intercom. At least you can share your music with her now. Alternatively, she can always listen to her own music (from her phone, ipod, etc.) while you listen to yours, albeit with no intercom to each other.
If there is a way for both parties to listen to music while also being able to speak to each other, I would be very much interested in learning how!