I don't think you need to forgive OW. You are free to hate her for what she tried to do to you and your family. I meant that you need to forgive your husband and you need to forgive yourself for whatever actions you may have done that made him feel unwanted. He he needs to forgive both you and himself. She's not part of this.
I don't think there is any chance she can think she's won if you tell her what you think of her or not. She can see, or hear from others, that you and your husband are still together and happy. And she can no longer work at his company. No, she is obviously the loser, and everyone knows it.