When stopped at a stop light, the rpms increase and the brakes must be pressed harder to keep it from moving forward. I'm not sure about when the engine light came on. I am dealing with second hand information from my out-of-town daughter.
Most places like Auto Zone, Napa, and Advance auto parts will scan a car for the engine light codes for free. Get her to do that and let me know what they say. With little information though, It sounds like an air leak is causing an erratic idle speed. Ask her if the engine RPMs rise and fall when the car is in park, or if its only with drive engaged.