Hunter, I am sure I would feel aggrieved too.
I do not brood on things but have them out in the open No Nonsense Nancy that's me) Sit down and write a letter, put it all on paper and either send it or burn it. Either way it will make you feel better.
MY sister and B-I-L got into financial trouble with the first Gulf War (they were in Kuwait) Nothing went right for them and I know that my parents and I, helped them out financially and in anyway we could.
I will say that until that point my sister and I were not very close but it brought us together in a way that nothing could break now.
Later, my parents felt guilty that they had given them so much and nothing to me. My sister also felt this way, but it really did not bother me.
It did make things tough for me. The children came here for part of their school holidays so sis could carry on working, I bought them clothing, helped pay for school trips.
Things are on an even keel for them now but with both girls at university I still help them with books. I don't have to but I enjoy it (until I get my bank statement!)
In return I have had the privilege of being part of the children's lives. They are good young adults with an excellent work attitude and a compassion for those in need. They will do well in the world as decent human beings and the fact that I had a small part in shaping them gives me pride.
There is nothing as odd as families, as the saying goes "God gave us our families, thank Heaven we can choose our friends"
Money is the root of much trouble, it can lead to jealousy and rifts that never really heal.
Personally I couldn't give two hoots about it. Not because I am financially well off because I am not.
Perhaps your mother feels guilty that her son died leaving a family financially troubled.
Perhaps she feels that now he has passed that she will loose contact with her grandchildren and this way she has contact with them.
Who knows. I sure don't.
Hugs to you because it is not an easy time for you when hurt by those that you love.