A neurologist was on GMA this morning with Diane Sawyer explaining the whole thing. He said that a bump on the side of the head is frequently more dangerous than on the front or the back.
Even a seemingly minor injury can cause the brain to slosh around in the skull, and tearing of blood vessels can result.
It's the movement of the brain within the skull that is the problem.
By the time the severe headaches came on, a lot of bleeding had probably occurred, with resulting pressure on the brain. Very critical to have the hematoma removed ASAP.
The blow usually tears the middle meningeal artery. This bleeds under pressure and peals the dura (blue line on diagram) away from the skull, compressing the brain and eventually causing it to squeeze through the base of the skull. It's common after the injury to have a brief loss of consciousness, then a "lucid interval" when the patient looks fine, before the final fatal sequence occurs. She sounds like she had a classic case....