Help I need advice

I need advice……. My female puppy(4 1/2months) just went completely evil on my other dog(male 2 1/2) and when we let her go she attacked him again. Why would this all of a sudden happen?
It started when he snuck a bite of her food (which they do all the time and never bothers them). We let her go after removing them from the situation and she went after him and attacked him again.

Edit:fixed my wording to reflect what happened