2nd on all this. She actually looks good. Get abx on board and maybe some meloxicam and i think she will do wellChickens can heal from some very serious wounds. It just requires time and care until the new tissue covers the wound. Meanwhile, she will need daily wound cleaning and keep the wound moist so that new tissue can be nourished to grow. Using a topical ointment will keep the wound moist. Powder may keep infection under control, but it does nothing to encourage tissue growth.
She would also benefit from an oral antibiotic such as fish mox 250mg once an day for ten days (amoxycillin) . Any time an animal attacks a chicken, bacteria is certain to have been introduced deep into a wound that may not be able to be flushed out completely.