I have two dogs, both are cross Beagle and Cavalier. The older one, a male, is 2 years old and the younger one, a female, is 1 year old.
5 months ago, my younger started attacking my older when he was near her food or when we gave him more attention. He doesn't retaliate and is scared of her when she does that. She even takes his bones and he lets her. Going near her would make her growl.
I believe my younger has self-esteem issues and wants to be loved, and we do love her. I give her first priority when I go outside (they stay outdoors) kissing her, hugging her all sorts of stuff, then my older. But she seems to want all of the attention. When I go to my older and give him attention, my younger goes near me. My older immediately leaves and does something else. A week ago I gave my younger half a treat, and was going to give her the rest, but gave it to my older. She became very aggressive and started biting him. Every time I have to hold her down very tightly or she'll slip out and start attacking him again.
The telltale signs of her anger before she strikes is that she looks at my older with complete focus, then attacks. She is smaller than my older. He has always been a passive dog, never biting. Even when someone hassles him, he bites but not very hard and only to get me to stop.
How can I fix her behaviour?