No. There's not much restaurant-wise on the airport perimeter except for a couple of lounges in airport hotels. Traffic can be miserable in that zone in the early evening.

Neither is there much in the landside portion of Terminal C -- not even a place to sit down really.

If you passed through security to see your friends you would want to be back in line to return airside at least 90 minutes before your DEL flight's departure.

The obvious option is for your friends to come in and see you -- have them buy a couple of fully refundable tickets on a late-evening CO departure, then you can go to a concourse bar until the last moment before you're needed aboard the DEL flight. After you leave, your friends cancel their tickets, get refunds, and walk out.