Ask your therapist if they are familiar with the standards of care. There are no requirements to live full time prior to starting HRT, or of having even gone out crossdressed at all. If they are not familiar with them, you may want to find a new therapist who is more familiar with the hormonal changes and transition process. You should not have to do anything you are uncomfortable with. As for HRT, some doctors will prescribe with informed consent and not require a therapist letter. Good luck!