I would say first and foremost: eliminate the trigger.
If she's attacking him over food, never have food with them together.
If she's attacking him over toys, play with toys one on one rather than between the both of them.
Not all dogs are going to be happy about any and every situation (sharing food, toys, etc) and there are ways to work with this, but in general, I would try to avoid the situations altogether.
I would also do some Nothing In Life is Free training with Amaya. Make her work for her food, just like you've done with Kuso. Make her work for her toys. Make her see that she's not entitled to everything she wants. With that being said, she's a dog. Her natural instincts tell her to protect her food from other dogs. Once you hand her food, no one should be near her, unless you give a successful "Drop It" command first.
Slightly off topic: I really hate it when people say "Oh he's so good, I can take the food right out of his mouth." What the heck are people doing taking food out of their dog's mouths? Have they no respect?! Any time I need to get something from my dogs, I give a "drop it" command. If this doesn't work with your dog ("your" used to refer to anyone, not the OP) then perhaps it's time to go back to basic training!
If she's attacking him over food, never have food with them together.
If she's attacking him over toys, play with toys one on one rather than between the both of them.
Not all dogs are going to be happy about any and every situation (sharing food, toys, etc) and there are ways to work with this, but in general, I would try to avoid the situations altogether.
I would also do some Nothing In Life is Free training with Amaya. Make her work for her food, just like you've done with Kuso. Make her work for her toys. Make her see that she's not entitled to everything she wants. With that being said, she's a dog. Her natural instincts tell her to protect her food from other dogs. Once you hand her food, no one should be near her, unless you give a successful "Drop It" command first.
Slightly off topic: I really hate it when people say "Oh he's so good, I can take the food right out of his mouth." What the heck are people doing taking food out of their dog's mouths? Have they no respect?! Any time I need to get something from my dogs, I give a "drop it" command. If this doesn't work with your dog ("your" used to refer to anyone, not the OP) then perhaps it's time to go back to basic training!