She must ask them to send proof that she agreed to auto renewal.
Not only should she have had the renewal notice prior to renewal date each year she should also have had the policy documents which make it clear she has 14 days to cancel.
What is the name of the insurance company?
If your mother is certain she didn't receive the renewal notices, the policies nor authorise automatic renewal she should contact the insurance ombudsman.
http://www.financial-ombudsman.org.uk