What Causes Blurred Vision And Headache After Having A Concussion?

My daughter is 14 years old and had a concussion (considered minor, but included blurred vision and projectile vomiting) a few years ago. About every six months, she will have a short spell beginning with the inability to read words or speak clearly and ending with a major headache. These incidences seem to happen when she has less sleep and is a bit stressed or is being very physically active. She also reports having VERY slight blackout moments about once a day, when she stands up. She is a very active volleyball player and her school work has not been impacted, as these headaches only last a couple of hours. Can you tell me if these are typical symptoms of a migraine? Are they common after a concussion and likely to disappear in time? Thank you.