My 2013 is the same. Your headset makes a difference. IE how good a quality and how close the speakers are to your ears. I use two different helmets with two different brand headsets. The one with the OEM Honda headset works better for me.
It may be the passenger's mic is too far away from her mouth. Have her have the mic just barely touching her lips. If that doesn't work, try plugging your helmet into the passenger plug, and have the passenger plug into the front plug. If the volume is the same as you are experiencing, then as I said it might be the passenger mic, or your earset.