What to do about psychotic girlfriend of ex?

If your ex is happy with his relationship, then you should leave him to it, it is not fair to you or your husband to have this woman in your life, she clearly hates you in hers. Step back let your ex know that if he wants you, both yourself and your husband will be there for him, tell him that all the time he is with his girlfriend, then you will step back as you hate how she is behaving and you feel that it is safer to be there for him but from afar. Discuss this with your husband first and tell him that you think it is for the best. This woman is obviously insanely jealous, and insecure, so just butt out of his life and get on with living yours perhaps you can get back to sanity and enjoy your life without all the drama. Take care.