The issue is not whether you can sue your ex therapist for termination of services but whether you would prevail if any lawsuit were filed and indeed litigated. Since you don't mention which type of therapist she is and whether she is a licensed psychologist, psychiatrist or family therapist, you need to understand the answer is not clear. While your therapist (to use the general term) owes you fiduciary responsibilities, I don't believe one of those responsibilities is to actually refer you to others but to inform you that simply he or she can longer be your therapist. This is not like an employer employee relationship. You may wish to look up the agency in Illinois that regulates and licenses your therapist and see if you can get some brochures or guidance on the relevant statutes that cover your type of relationship and what she owes you in terms of her fiduciary responsibility, from beginning to end.