I'm afraid this happens far more often than it should; one reason I wanted to reprint your letter was to remind each of us to be more concerned for those who've lost a loved one, or experienced some other trauma.
Why do people react this way? Often it's because they've never gone through the experience of losing someone near to them. As the result, they don't realize how devastating it is, or how lonely someone may be who has lost a spouse or other loved one. Often, however, people feel embarrassed or inadequate; they don't know what to say or do. Or they may simply be preoccupied with other things and don't stop to think about the needs of others.
The Bible, however, urges us to show kindness and sympathy to those who are hurting - whatever the reason may be. It says, "Be kind and compassionate to one another" (Ephesians 4:32). It also tells us to "Rejoice with those who rejoice; mourn with those who mourn" (Romans 12:15). Perhaps God wants you to reach out to others who are suffering, and be a friend and encourager to them.
The greatest truth I can give you, however, is that God understands your grief, and He is with you every moment of the day. Turn to Christ at the beginning of each day, and thank Him for His presence. Thank Him also that because of His death and resurrection, death has been conquered and He has opened heaven's door for us. Is your faith and trust in Him?