I would deffinatley rehome gwen, so that your other 2 dont become scared and nervous, or end up getting seriously hurt.
Gwen should be placed in a home as a only dog, if she behaves this way. However how does she get on with males?
I have attached a pic of my old baby boo, that i sold back to the breeder at 9 months old(i had him since he was a puppy),as he picked on Duchess. She became very reserved and frightened and i didnt like her being like this. He is now happy at his new home and Duchess is back to her beautiful, cute, adorable and funny little self
It was hardest thing ive ever done,i loved that baby to death,but it was the right thing to do.