don't know how to guess what caused the situation, rooster or predator. observation is the best way to tell. but for now you need to make sure that wound stays clean and heals. I agree stitches would be best for the big laceration. I don't know what the next best thing would be other than cleaning often, using an antibiotic ointment maybe, but please check with others here on what would be appropriate. oral antibiotics would be a good idea if you can get them, make sure it is good for birds and you have the right dosage. clean the wound as often as possible with diluted warm betadine. i would follow with a quick spray of hydrogen peroxide if you see ANY flies, as this will kill larva (MAGGOTS). keep her separated from the rest. make sure after cleaning the wound she is dry and warm. is she eating and drinking?
good luck, i hope she recovers!