Does it seem like she is losing blood through it, or is it just a blob of bloody substance?
Try to put something on that area to prevent any bleeding. Flour can work for that, it can clot blood.
Keep that chick away from any other chicks. It would be good to keep it in the incubator as long as you can to hopefully increase chances of that drying up and possibly falling off. Even if you have to seperate a small area for the chick where other chicks can't get to it.
I have never experienced any chicks this bad, but I have had a couple bleeding after hatching, so I stopped the bleeding best I could and kept them in the incubator and they all were back to normal pretty quick. But mine was not as bad, so there is no guarantee.
And if they make it to being able to walk around and dried off, it would be good to get some vitamins and electrolytes into them to keep them going and hopefully give her a health boost.