Recently my mother aged 63 went to chennai alone. There is nothing to worry. Contact the airline and request for assistance atleast a day before. On the day of journey request for wheel chair from security and you can accompany your mother till geting a boarding pass from the airline. Then the airport staff will takeover through the immigration and will leave her in the gate. Again when the gate is open airline staff will take her to the flight. Absolutely nothing to worry. When flight reaches cochin again the airline staff will take her through the immigration process in india and accompany her till she is handed over to some one in cochin.
All you have to do is inform the airline and request for a wheel chair(irrespective of her fitness)