Congratulations on a beautiful and engaging post, @malloryblythe, I thank you for inviting me here :-)
The Golden Rule works through all cultures and religions; I haven't seen a religion yet where this rule is not mentioned in some form. This is just one of the countless indications of the observable fact that we are social creatures. As a materialist you will be interested to know that your brain and nervous-system contain lots of mirror-neurons. These are neurons that fire when you act, but also fire when you see someone else act. These cells are the material with which we learn and they are the materialization of this Golden Rule. The mirror-neurons in my head paint a painful face on me when I see another man being kicked in the nuts real hard. I don't feel the pain, but I act as if the kick landed in my own nuts...
You know this already, I think, but I think we live in an era where we are constantly reminded of the opposite; we seek freedom on an individual level and that's just not realistic. You may be surprised that one of the best descriptions of freedom comes from Marx. He knew that capitalism, with all it's advantages for accelerating material wealth that he saw and admired, it would alienate us from our humanity. He saw as the main difference between humans and the rest of the animals the fact that we do things for other reasons than just survival. We do things for fun too. We dance, we paint, we make music, books and movies to entertain each other, to communicate emotions, thoughts, ideas...
While some aspects of capitalism have the ability to maximize our exclusively human traits, it does the exact opposite, and Marx saw that coming. It forces us to keep working for our needs, instead of freeing us from them. The worker, the laborer, the employee basically has two kinds of relationships in this system: a competitive one with his colleagues, his peers (rather he lost his job than I lose my job), and a master-slave one with his employer.
As an individual we can never be free: in that sense freedom simply doesn't exist. Freedom, whatever you may think that means, is only to be found in your relationships with other people. As an individual you are doomed to constantly worry about survival, only in large groups we are able to free our self from the shackles that our basic material needs impose upon us. We have build a system however, in which all that counts is the individual. That's why some people truly think that to be free means to be free from the arbitrary will of other people. Freedom to do what you want when you want to do it.
The way I see it, you're not a materialist. I am not a Marxist. We don't have to be categorized in order to realize we're all human beings and we're all not alone. And our freedom and happiness lies in the realization that both are only to be had as a community of social creatures. The bigger the community, the larger our freedom and happiness. But not, never on an individual level. The freedom of that individual as well as it's ability to optimally develop it's true talents, are dependent on other people.
And that's what struck me most about your touching account of your grandmother's last moments in this life. She didn't die alone. She was widely admired. So she apparently touched a lot of other souls and brought them happiness. She brought you happiness till her last moments, and you made har happy too... And she still does. And through you she now brings happiness to all of us enjoying your writing talents that makes us experience a tiny slither of the love between the two of you. And there's nothing materialistic about that ;-)
Sorry, I tend to rant... All the above is of course just my opinion. You are a beautiful soul, @malloryblythe. No other information is needed in my book :-) Thanks again for inviting me, I had a very pleasant stay, thanks to you and your grandmother,and I thank you both!