I am reminded of a story about Wayne Gretzky that I heard years ago that, if he were riding an elevator alone and an attractive woman entered alone from another floor, he would step out of the elevator to avoid any possible 'stories' that may have occurred whether he did or did not do anything.
I am a bit of a giant at 6'5" tall and my work requires a fair amount of physical strength. Since I heard that story about the Great One, I try to follow that modus operandi as it would likely make the girl feel better than to have a burly fellow in close quarters, and it removes me from any liability if I'm accused of anything.
The only crux to it all is that I trust myself, naturally, but if someone else gets into the elevator with the young lady with malicious intent, I'm no longer there to protect her (I'm a dad, it's inherent in me)