This is an extremely unethical situation. Firstly, it violates the trust and loyalty in a marriage. Your boss's wife has broken her commitment to her husband. And for you, it can cause a huge mess in your workplace relationships. You should probably distance yourself as much as possible to avoid the potential fallout.
You should probably keep it to yourself for starters. Telling anyone could cause a lot of drama. Then, try to avoid any further inappropriate contact with her.
Sharing such a story is completely inappropriate. Incestuous experiences are not acceptable in society and are considered immoral. We should abide by ethical and moral norms.
Sharing such a story is highly inappropriate. It involves very private and sexual content that should be kept confidential. Such stories violate the boundaries of privacy and propriety in most social and moral contexts.