I think if you WEREN'T angry about this I'd have to check your pulse. Anger is a normal human emotion. I know that sitting in perpetual anger is bad for you emotionally and physically, but that isn't what you are describing. Be angry and don't allow him to discredit your valid feeling after he did something so awful and she continues to do what she is. Is there any way you can remove yourself from that environment?
Big hugs...thats just awful.