So sorry to hear about this. I am sure that this is a hard time for your family right now and our thoughts and prayers are with you.
As far as insurance goes you may find yourself singing Obama's praises soon. Under the Affordable Care Act anyone with a preexisting condition may apply for health care exchanges now if they have been uninsured for at least 6 months and denied health care insurance due to a preexisting condition.
Here is some information on the program: http://www.healthcare.gov/law/features/choices/pre-existing-condition-insurance-plan/index.html
My advice would be to apply to a private insurer (with the knowledge that you will likely be denied) and then start the paperwork to collect insurance through the exchange.
That being said this should not stop your mother from receiving adequate health care. Every major city has a hospital that will treat uninsured individuals. Just walk into the ER and ask to see the Dr. and you will be seen. They can direct you to social services which will be able to help you out.