A concussion, as found on Google, is a "temporary unconsciousness caused by a blow to the head.", which means a really hard hit to the head, and then a knock out or a blackout
Some symptoms that are usually associated with a concussion can be but are not limited to: headaches, memory loss (if severe), nausea, vomiting, slurred speech, confusion, and fatigue. There can also be sleep disturbances, sensitivity to any type of change, such as air or light, and disorders of the 5 senses (sound, sight, touch, smell, and taste).
Answer:
This isn't a health question but...
It's possible she didn't like what she saw in you when meeting in-person. This isn't entirely uncommon in friendships (and more).
Give her some time and message her again. But if she says stop, stop.
Explanation: