Chick with sore / bump on neck, and erratic behavior / movements- HELP

We got our chicks a few weeks ago, everyone is growing as expected, but one seems to be much smaller than the rest.
i think she might be a barred rock...

A week ago, i noticed that she had a bald spot on her neck, and it seemed there were also some melted or burned feathers on her neck too. i figured she must have jumped up to the heat lamp in the brooder and hit her neck on the hot lamp. She was acting normally then, and for the week or so after, but just today i noticed that the bald spot on her neck has a sort of bloody sore with a lump under it. and she is acting very weird, trying to peck at something nonexistent under her neck constantly, to the point where she pecks so furiously that she tips over. she continuously does this, scratching and flailing, scaring the rest of the flock. when i pick her up she calms a bit, but then she seems to calm too much, and her neck almost goes limp and she sits for a moment, but gets back up to try to peck under her neck again. she seems a bit like she has gone a little crazy (crazier than usual for a chicken) and pecks at things with no idea of what she is doing.
I am afraid she wont make it.... could she have a tumor or something? should i separate her from the other 11 chicks, or how else can i help her??

Here are some pictures of her neck, her compared to the other chicks (she is the smallest black one), how she gets all still in my hand, and a video of how she is acting..... i hope any of it can help..... i dont want to lose one of my first chicks we are very attached.........

thanks in advance to everyone....
Jessica
(Video Link here: http://db.tt/rp1lfdVy )