There is indeed a difference in being incompetent and being disabled.
In most states incompetence is a legal issue and can only be decided by a judge in a court of law.
Disabilities do not have to be decided by a judge in a court of law unless the disabled person is applying for compensation of some sort.
However, in most states, we, as nurses, are charged with acting in a prudent manner and in performing to the highest level of our education/abilities. If, with reasonable accomodation for her disability, she cannot perform in a manner safe for the patient, this needs to be addressed.
What can you do? Document, document, document any and all instances of unsafe occurances. If it is not documented, it did not happen.
Meanwhile, be as kind as you can be while remembering that, above all, you are the patients' advocate.
Good luck to you. :heartbeat