Hello,
There is a new regulation on the passengers from India who is travelling to Qatar with the "free on-arrival tourist visa". Some of the airports in India (not all, Hyderabad started first) is not allowing the ECR passport holders to travel to Qatar without a paper visa.
Since your mother has a valid issued visa, it wont be a problem. However, it would be better to talk to the Airline or Immigration office in India and they can provide you clear information.