Agressive female/laid-back male pit

Question
We have 2 pit puppies that are 12 weeks old.We got them when they were about 8 weeks.Sadie is the female and Blue is the male.Over about the last 2 weeks Sadie has become very aggressive towards Blue and attacking him for no apparent reason.Blue doesn't fight back and its almost impossible to get her off of him.What can I do besides get rid of her to stop this behavior?Will Blue end up with this same aggression later on??Help!

Answer
Get them both into obedience classes right away. Have them spayed and neutered as soon as you can get a vet to do it, especially the spay. Some vets will do it at 16 weeks and surely they will neuter at that age. You ended up with an alpha female most certainly.  Either you get it under control now, or you're in for serious problems. I doubt the male will end up the same way, but eventually he will defend himself if this continues.