Know it may be a bit late, and I'm sure some people already covered this but I am lazy. With all of my ex's I tell them that what ever way we cornering they need to look over that shoulder. ie. right turn they should look over my right shoulder. Makes it a lot easier for them to keep it in mind with a simple goal like that. Work out some signals ahead of time too, tell her she can tap you right leg to go faster or left leg if she wants you to slow down. Same for you, think of some basic motions to let her know what your intentions are, such as passing, accelerating, etc. Without headsets there is no way to talk other than hand gestures. If they are a good passenger you shouldn't (from my experience) feel like they are really there. Just be sure to slow things down and don't be stupid.