This is an integrated question that requires gross, neuroanatomy and some pharmacology to answer correctly. Nevertheless, it is a good board type question.
This patient has peripheral facial nerve (CN VII) palsy caused by trauma. While the forehead receives bilateral innervation, the ipsilateral forehead is only spared in central facial palsy (see figure for explanation). Because this is a peripheral facial palsy, she will not be able to move her forehead on the ipsilateral side. In addition, her delayed presentation (e.g. one day after the event) is likely due to edema within the facial nerve canal. In this case, corticosteroid therapy can control the edema. Acyclovir, on the other hand, is an antiviral medication that works by stopping the spread o the herpes virus in the body. But the palsy, in this case, can be clearly traced to trauma. If her facial nerve palsy fails to improve with corticosteroids, surgery can be considered to decompression the nerve canal.
Answer to this question is based on material presented in lecture 4 in Head and Neck series.