History of brain abcess caused by sinusitis went to ER with head pain she had CT scan they said brain was fine. However her forehead has swollen.

Change? If the forehead swelling is a significant change from the exam on the day the CT scan was done I would go back to the ER for a recheck.
Need more info. Besides the headache does she other neurologic symptoms? Does she have a fever, chills, and/or night sweats? Did she have a lab eval and what was her white count? How long ago did she have the abcess? Do you know the organism that caused her abcess? Does she have any immune deficiency that predisposes her to recurrent infections? If there is any question of her status then go to the er.