I've met many people fearful of being hit by the ball at the net. It's understandable since it can hurt but like anything, you can train yourself out of the fear. Excellent doubles players that I've met sometimes don't like the risk at the net initially, so here is an approach.
The student is afraid of balls hit at them with pace from the baseline when at the net? If so, I'd try reflex drills face to face at the net where body shots are part of it with increasing speed. Sometimes you get hit. The only big risk up there is a head shot and usually, your head just needs to get out of the way to let a ball fly out since a high ball at high speed means it my fly.
Learn to use the racket face for self-defense from the ball at the net and over time make it the tool of replying to the shot as well.
