On the one hand, dc wants to put it behind them. They are not responsible for the bully's behaviour, so why should they be obliged to engage in any way with it?
OTOH listening to (or, in this case, reading) an apology and responding gracefully is an important life-skill.
So should I give dc the letter of apology, after they have said that they don't want to read it? A month has passed since the incident and since the letter was written.