I would agree that it would probably be best if she wasn't there. If she already is a close friend of his that may be a different matter though, and if he knew she liked him, but the last thing you would want to see is that when she is rolling she gets a bit too friendly, and he isn't ready for that. I'd hate to see him come away from this thinking she used his grief and time to talk about his issues as her attempt to get closer to him. Even if those aren't her intentions, and I am not saying they are her intentions, he may interpret it as that.
I feel if your female friend is there, I'd be completely upfront with how she feels about him. I know if it were me I'd feel tricked, set up, even if the person who liked me never even attempted anything. To me it would feel like someone was taking advantage of what I was going through in order to get closer to me.
But otherwise I think it would be a great time for him to maybe gain a bit of perspective back on his life. I know recently I had gone through some awful stuff, and was feeling heaps down, not myself....and a night on ecstasy helped to clear my head. I find it gets me to really get to the point of what the exact issue is thats upsetting me, and get rid of the trivial stuff around it, thus leaving me able to deal with the real issue properly.
Good luck with it all, let us know how it goes.