Oh what a horrible thing to happen. Words cannot express how sorry I am for you all going through such an experience. Try not to feel any guilt - it was not your fault, you could not possibly know how she or the dog would behave. I too lost a cat, my Napoleon, horriblyu of poison just a few months after I brought him across Europe to France from Bosnia, and I know the hopeless, helpless feeling of uselessness that invades you when you have tried so hard to give your kitties hte best possible chance in life.
All my sympathy and thoughts are with you
All my sympathy and thoughts are with you