Katie your mom sounds like a very angry person to me. Her history as you describe it, is that of a person who was treated as a throw away at a very young age.This anger may have been the only tool she had to survive. Then since it worked for her at that time, it becomes the only emotional tool they trust.
A person can become so familiar with this type of treatment, that they believe they deserve it and that this is how their life will be and this is who they are.
To remain who they are, they accept people who will abuse them and fit right into the jw cult and other like minded groups.
Since they received so little love in life they do not know how to deliver love. It is not comfortable for them to love OR BE LOVED.
There are also some mental problems that cause this behaviour or this kind of life can cause mental problems, Bi Polar is one that comes to mind.
For your own well being, you might consider " not expecting anything from her" and look at it as something she is incapeable of doing. As we would act if she had a physical problem such as we would if a person could not hear. It is impossible for them to start hearing.
You might "love her from a distance", love her but keep your distance or accept her actions as what she will always be and do not let it hurt you.
I have still to learn, to change the things I can and to accept the things I can not change. But I will say that this is something to consider.
It is always comforting "especially after some one has passed away" to know that you kept the high road and was always kind and helpful.
Outoftheorg