A week ago our 15 yr old daughter was outside, passed out, fell and hit her head on a rock. It took about three hours for her to start acting like herself. They checked her in the ER, thankfully found no brain bleed but said she has a severe concussion. I feel like there's something I could be doing to help speed healing. She has a severe headache all the time, which Dr. said could go on for several weeks or even months.
Looking for ideas of what has been helpful for other people, especially teens.

Unfortunately, there really isn't anything you can do. She needs her rest and time. That's it.

It's not something that she should try to "work through." Rest helps the brain heal.

When my son had a severe concussion, our Dr. gave us a list of things to avoid to help with the headaches. Call your doctor and ask for his list to ensure healing.