Withdrawal from daily routine and social contacts are the big clues. The burden of loss and the feeling of hopelessness will set in. Soon to follow is anger. The anger is generally directed at the deceased, the doctors, the rescuers, God or the survivor herself. Thankfully, following the anger period, acceptance is discovered.
Life starts to get back to normal.
Discussions of the future begin to take place. Recognizing these stages will assist you in helping your colleague. The sooner the survivor can release their feelings, the sooner the impact of those feelings can be significantly reduced while still fresh in the mind and not clouded by time and subsequent emotional reactions. While listening, do not judge, try to solve, try to fix or make it all better, or discount the feelings of the speaker. You cannot make it all better.