Is Gorilla Glue Challenge is dangerous?

Does it matter?
It's idiotic, regardless.

Also, the reason she was hospitalized was because of what was done to try and remove it.  If she had either allowed her hair to grow out, or just cut it off (as many a parent has had to do with a child) she wouldn't have needed medical attention.

Why would anyone be stupid enough to do that?

Yes, it's dangerous. You can end up in the ER.

Yes if you use it in or on your body.