I think everyone is right here. No one is arguing that the neighbor's dog has a right to be wherever it wants, or that the loss of our chickens isn't tragic, or that the evil neighbor is actually a hero and a good neighbor. It's just that life is extraordinarily complex, bad stuff happens, we can't possibly prevent it all, even when we think we're doing everything we can to protect ourselves and those we love.
But when bad things happen it is good to be able to learn something from it, and to grow, and to move forward with better plans, regardless of who was right and who was wrong.
The original poster was angry and heartbroken, and rightly so, in her care for her child and her chickens. But pushing all of the responsibility for life's trials away from ourselves and not taking the care to identify what our part may have been, even if it was a small part, so that we can change it and become better is necessary if we don't want to always live like victims. It sounds like she is taking responsibility for her part, and planning some changes, and that's a good thing, a strong thing about her. Please don't take that away from her.