Your response to her telling you that she doesn't know if she can stop talking to him, has now allowed her to move forward with the affair. Expect it to become physical. You have now told her (with your actions) that its acceptable for her to cuckold you. You have opened yourself up for a lot of pain.
What you should have done, based on her last comment, was to tell her that you will be seeing a lawyer and filing for divorce. Then you need to expose the affair to her family and your family and friends. Separate finances.
If you have already taken these steps. Please ignore this post.