I'm sorry to say this but you havent provided enough information to help you point towards an inheritable disability. The only thing that you've mentioned could be an indication of dyslexia but dyslexia is often found in any number of disabilities. Though dyslexia makes learning to read, write and spell more difficult, their IQ is usually no different to anyone elses. You can be gifted and still be dyslexic.
If your mother was born with a low IQ or sustained an acquired brain injury in her childhood, that could account for her child like behavior, first is inheritable the latter, not.
Still way too difficult to help you answer your questions, sorry!
Welcome to the MedHelp forum!
Reading and spelling problems are usually due to dyslexia and often there are other problems associated with it. It is of three cognitive subtypes: auditory, visual and attentional and is basically a reading and learning disability. Your mother needs special care where she can be taught to read and write. This is not hereditary.
Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!
I am going to suggest you try something very simple.
When you visit bring a patch and put over her left eye. Try to have her read.
Then do the same with the other eye.
I do some work with a psychiatrist and he had a patient with a problem in the corpus colusum, and with both eyes open the patient became totally confused with words.
Such patients can be taught to read and write, but it takes patience. Don't give up on her!
And value is measured by much more than the ability to read and write.
The life-force has it's reasons.
People with disabilities often have more love to offer and can be more rewarding to work with than others with far higher abilities.