Given that it is a training experience, but you are also supposed to be getting helped, I agree that it would be appropriate for you to thank her for what she has done for you. That said, then maybe add, "I believe I am now to the point where I need to be more independent with my life. I appreciate your being helpful by offering your guidance on (whatever), but....." Or something like that. I can't imagine she would terminate anybody for now being able to be more independent!