I'm similar to BWStearns, I let my girlfriend monitor facebook for events, we often both get invited to events where only one of us attend or one of us is invited by the other isn't. That's not to say she manages my calendar. We have both our own GCals (viewable by the other) and a shared GCal, we've had a long standing agreement that if we book anything in our own calendar attendance by the other is not expected and our shared calendar is attendance optional unless otherwise specified.