What is causing my client’s heart symptoms? Is it dangerous, and what is the best treatment?

Your intuition is spot on here. She is suffering an inner emotional turmoil that gets her going. That is all that is taking place. It is not dangerous and it needs no particular medical treatment. You, of course, will be taking some risk sharing this with her should some new issue or problem develop and she were ignoring medical advice. There is little you can do in this kind of situation. As usual, she is hostage to her fears and this will govern her choices most likely, going forward. You cannot force things on her and there is always risk in providing guidance as a non-physician. This you will understand, so we are confident in giving you this feedback because we know it to be true. That does not mean it can’t be used against you in some way.