Luna could have a very calm and unique reaction. She might start talking about some strange magical creatures that are known for their healing powers and suggest looking for them. Professor McGonagall would be very concerned but also very practical. She'd use her skills and knowledge to start treating Hermione's injury right away, while also making sure the other students are safe.
Harry would probably be extremely worried. He'd immediately rush to her side, trying to figure out how to help. Ron, on the other hand, might be in a bit of a panic at first but then would do whatever he could to protect her while waiting for help. Hagrid might bring some of his home - made remedies, thinking they could work on her injury.
Draco might have a more complex reaction. If he's in a situation where he's starting to change his views, he could be secretly glad she's not seriously hurt while outwardly showing a bit of indifference. But deep down, he might respect her more for getting injured in the face of danger. Neville would be very sympathetic and would offer to help in any way he could, like gathering herbs for a potion to heal her if that was needed.