Bube, I apologize for coming on so strong. I know you're a level-headed guy trying to survive in an untenable situation. It's hard for me to hold onto myself where animal abuse is concerned.
The point I was making is that-- even if what BF says is true (that your D hates the dogs because of how important they are to your W (and this makes sense)-- to express hatred, resentment, anger with physical violence toward a helpless, dependent species is a major red flag. Even if she had gotten intoa fight with her sister and punched her, that would have been bad, but maybe a two alarm red flag instead of a four alarm red flag.
To take that anger out on a creature who is not permitted to defend itself (e.g., by biting) makes ME want to throw up. To WANT to kick the dog is totally understandable; to cross the line and actually DO it shows a moral compass that is haywire. Your D is screaming for help.
What if she had killed the dog in anger at your W? How would you rationalize that? How much worse does it have to get?
Sorry... there I go again... probably projecting, too.
Your sitch makes me hurt more than any other one on this board. I wish you peace, my friend.