I can only suggest you few things but the best thing for you to is to contact a solicitor who specializes in Immigration matter. I believe your mum would come under the exception rules and this should be done through a Solicitor. It can be successful if you do it your self with all the letters from Doctors and places where she took English courses.

One thing you do need to keep in mind is teh time period.  I believe it is 5 years unless she came on the marriage basis then it is three years.

You may be able to avoid extra hassel if you see that she can pass the test. I would suggest at least let her try.

just let her attend ESOL Class end of the years the college will produce her a lettre or certificat to say she s done the citezenships text thanks good luck