Very tight
If the international flight arrives ahead of the schedule, there is a chance to make the connection because EWR-DCA flight leaves from Concourse C. There are two later flights on ERJ145, which depart from Concourse A (taking a shuttle bus from ~C70 Gate).
Here are some possible actions:
1) Check the time and the flight schedule;
2) if there is more than 40 min before the scheduled departure of the booked EWR-DCA flight, go through the security at Concourse C and run to catch the flight (no stopover anywhere!);
3) if there is less than 30 min before the scheduled departure, change the ticket to a later flight or next day flight at the luggage re-check place. If they really want a flight with first class seat, they should think of spending a night at NYC or re-routing to IAD (Washington-Dulles).
4) If they have to take the later flights, take the AirTrain to Concourse A and pass the security there.
Good luck.