I have a 4100NEX and a GLI with the iDataLink Maestro. I don't believe that I've set the handsfree setting at all, and mine works with both the VW integrated bluetooth as well as the AVIC bluetooth, even simultaneously. I have a work cell phone as well as a personal one, and I can have my personal phone connected via Android Auto (which uses the AVIC bluetooth), while my work cell is connected to the VW bluetooth.
I suspect that the issue lies with your phone (or your wife's phone) choosing to connect to the AVIC bluetooth rather than the VW bluetooth. You should either remove the phone
