this is typical female budgie behavior. put the aggressive bird in a cage by themselves, close to the other cage and allow them time together to fly around the room together but give them their own cage, this is not a punishment, keep that in mind, you are simply giving them the space they need. females become hormonal, like all females, and sometimes they get sick of each other, ive had to do this with my females and after a week or so of being in their space they are ok to go back, but possibly she might enjoy being in her own cage. one of my male cockatiels is in a cage by himself, because he is grumpy and hormonal, a very happy bird, he just likes his OWN space and he comes out and plays with the others but goes back to his own place and he likes that.