My two female birds are fighting

Question
I have 3 zebra finches about a year old, one male and two females. I hand fed them so they always fly around the house. Recently, one of my females started to bite and peck my other female. she is doing this every single time that they fly out of their cage and even in the cage. I have put this female in another cage so that she doesn't bite my other female anymore but still, when they go out, she always bites my other female. Please tell me what I should do about this.. Thank you, Claudia.

Answer
It almost sounds like the bully female doesn't like the idea of another female around the one male. This can be solved by making sure the females are always separate (including free flight time), getting another male, or getting rid of the bully female. You can also try adding fake plants to the cage to create some visual barriers but since she bites the female when they are outside the cage, I don't see this helping.