You need to isolate her for her safety as @Kmaria187 pointed out.
I've had good luck "gluing" the torn comb back onto the scalp with triple antibiotic ointment. Clean the wound with saline. This is important to set up the correct pH so the tissues will "take".
Squeeze out the ointment onto the scalp and lay the comb back in place, then put an ample amount of ointment over the top to hold it in place. Keep her isolated until the comb is solid. It shouldn't be longer than a couple days and it should be growing back to her scalp.
You also have the option of completing the "dubbing" by simply cutting the loose part off. This may be advisable if she is continually getting bullied and injured. I had to partially dub the comb of a little Wyandaotte hen that the others were repeatedly tearing her comb from her scalp. It healed quickly and she had no further problems with getting scalped.