Sorry to hear about your wife's accident.
Normal motor insurance policies usually cover use of a vehicle for "social, domestic and leisure" purposes, including travel to and from a fixed place of work.
Business use is covered by Class 1 and Class 2 business use policy endorsements on non-commercial vehicles which include the carriage of goods and samples and the use of the vehicle to travel to business appointments away from "base" where the employer pays business-travel mileage.
IMHO, if your wife was not being paid a car allowance by her employer and was en route to a social event (family visit) it would be hard to argue that she was not adequately covered at the time of the accident.