Yes, people can be greedy, and sometimes greed is seen at its worst when an estate has to be settled. One reason I wanted to reprint your letter is because it points out a problem that occurs far too often -- and one that could have been prevented if your mother had planned ahead.
The problem is this: Undoubtedly your mother knew what she wanted done with her things, but because she failed to put it in writing, it's caused much disruption in your family. But this wasn't God's plan; God is for peace and harmony, and He wants us to do all we can to prevent such conflicts. The Bible says that "everything should be done in a fitting and orderly way" (1 Corinthians 14:40). This is why I urge people to seek God's wisdom about these matters and to have a valid will.
I realize that for you all this is water under the bridge (so to speak) -- although I hope it will encourage readers to put their own affairs in order. But the question you face is this: What can you do to help your family overcome its conflicts?
It may not be easy, and it may take time. Ask God to help you be a peacemaker with your family. Reach out to them, not dwelling on the past, but looking to the future, and letting them know you care. Pray for them also, asking God to change their hearts.