As far as I'm aware Tricia - no, unless she has some impairment/disability that would qualify; but receiving AA on it's own is not a qualifying factor.
If your Mum lives alone she should get the 25% reduction in Council Tax that all single households get; if you live with her and are her sole carer then you should be disregarded for Council Tax purposes.
The only thing I know for sure is that if she has a mental condition she should be eligible for a further reduction - but it seems that most local authorities have their own rules as to what constitutes a mental condition.
I would suggest that you get the forms from your local council, fill them in and see what happens.