You should live dangerous and turn your head toward her--put your finger in front of your mouth and shush her. The look on her face is always priceless. In answer to the O.P. ---my passenger almost always slides into me and tries to stay on the bike while following the bike as I maneuver to get us out of a situation.

 

Dig in with their heels. We may need that extra inch of stopping power!

 

I never had to make a real emergency stop with a passenger. But like the one poster said... I'd think to dig in with the heels would be what I'd say. More or less what I just tell a new passenger. When we are coming to a stop sign, or light, Put your weight on the footpegs and hold your weight back off me. I don't know about the grab bars, my bike does not have them, nor a backrest. I think the footpegs are a big thing. Passenger should put weight on them and then maybe they would not be slamming their helmet into you, etc. I took the passenger seat off my bike, but that does not keep people from asking me for a ride. I thought it would, but it didn't work.
NTGIRL

 

I got my skills from my Dad. My brother (who's 11 years older than I), however, was not home that day and missed out. So when growing up, I always had to ride on the back with him to go anyplace. He wrecked often. I, having enough knowledge to recognize that he was about to wreck, would usually jump off and save myself.

For my passengers, I just tell them to hang on and stiffen up their legs. That helps keep them from sliding into me, and causing me to slide up the tank.

 

Sit still, shut up, keep from banging helmets and keep their feet on the floorboards!