if the incoming flight is on time then its doable....however, keep in mind that they will close check-in for the outgoing flight an hour before the flight so you will have to cross immigration, collect baggage (if your mother is checking in baggage), leave your mother with your relatives & make it back to the check-in counter in about an hour if you are trying this in del....for this reason alone bom might be a better bet since you get an extra half hour there....