Her comb looks like frost bite. Do you have ventilation in the coop? If there isn't enough ventilation, the moisture from their breath condenses on their comb and freezes in cold climates and the comb starts to turn black. Vaseline on her comb should help but ensuring good ventilation is important.
The wound on her back looks like pecking. How big is their coop? If they are used to being out in a run or free ranging and are now confined, that can lead to boredom and pecking especially if space is tight. You need to clean it up with antiseptic and cover it either by spraying with Blu Kote or preferably making her a chicken saddle/apron/cape as that will give her better protection both from the other hens as well as the cold.
Chickens can kill each other if they open a wound up, so you need to take some action to protect her. The Blu Kote spray disguises the wound by making it blue/purple instead of red.
It may be that a higher protein feed will help prevent further pecking but giving them things to occupy them, like hanging greens or giving them toys should help. A simple toy can be made by putting some scratch grains into a plastic bottle and cutting a very small hole in it so that when they roll it around only one or two grains come out. A non glass mirror may help make the coop look bigger and also distract the bully into thinking there are other strange birds in the coop that are more worthy of her attention. Perches to jump up on or boards leaned up against a wall to hide behind, so that bullied hens can get out of sight of the bossy ones can also help. A similar situation can be created using a curtain, ie. making a screen for the victim to hide behind. Multiple feeding and water stations also helps. Make sure that you don't create any dead ends where a chicken can get trapped and bullied more.
Good luck sorting the problem. Chickens are pretty hardy so I think your girl should recover from that wound fine but you need to prevent them from opening it up again as that could be fatal. If you decide to remove her from the coop to allow her time to heal, you will find reintroduction much more difficult, so protecting her within the coop is best.