Scattered foci of increased T2/Flair signal indicate small vessel ischemic disease or changes of brain blood vessels. In your daughter’s case, these could be due to the accident, high blood pressure, migraine, either individually as a cause, or a combination of these conditions.
Also since she has headaches and ringing in ear, a lumbar/spinal tap should be done to rule out beningn intracranial hypertension due to impaired CSF absorption.
Headache with tinnitus or ringing may be stress related or due to sleep disturbances. Subarachnoid hemorrhage can also give headache with tinnitus so since there is history of head injury get this investigated. It can be a chronic daily headache which is a variant of complex migraine. It can also be due to carotid artery kinking, aneurysm or blockage. High BP could be another cause.