female dog PMS?

Question
I have a 2 year old Aussie who should start bleeding with her cycle any day now.  she has become very aggressive to her 'best friend" our other Aussie a male 10 year old.  She has attacked him twice already today with no provocation from him at all. Is this aggression normal? It seems to get worse with every cycle and we are breeding her in summer. How can we keep her from fighting with him? What can we do to help her. it is out of control. Thank you, Dina

Answer
Dina,
If you are planning to breed these two, you need to separate them.  If they live as brother and sister they sometimes don't breed with each other.   
Two things could be going on:
One,  is that she is two and at that age, they become a lot more aggressive toward other animals.  They get jealous and try to become alpha.
Two  she may be having a sort of pms and since she is living with the male, she may not want to breed with him so is warning him away.
nancy