There is a key that you can press to highlight all characters on screen. I really dislike the effect because it is 2D and thereby ruins the 3D experience, but it does its job at knowing where everybody is at. I believe the key with the accent grave and tilde symbols is the default.
All the best to your friend! Chemo sucks, even though playing video games is a nice way to pass the time when you can't do much else.
