My failure as a foster mom

I understand you. I have three rescue dogs, two of them are therapy dogs. They are very tolerant and loving. If someone hurt them purposefully, I imagine I would feel the same way as you do. That is actually on my list of "no-no"s, (known abuse of animals). My dogs are rescues and know abuse and neglect themselves. My home is supposed to be the healing and safe haven from that previous life. I would be very angry as well. I guess my best advice is "fake it until you make it" for her birthday today. Keep her in line of sight until she leaves in a few weeks, so she won't have an opportunity to harm the cat again. And of course DOCUMENT.