A rescue dog I took in was extremely timid at first shaking in a corner of her kennel for weeks and not looking at anyone. Using the pack mentality she came out of her shell and played with the other dogs. Now she has gradually developed a sneaky aggressive attitude towards them and behind my back because she knows its wrong bites them on the neck to the point I had to put her on an overhead so the other dogs could get away from her. Because she does it on the down low I only hear it when its over so cannot correct immediately and when I go out there to check on the dogs after the incident she runs and hides knowing she did wrong. She gets exercise and equal treatment with the other 4 dogs. She never does it in front of me. Im stumped on how to fix this.