I may not be understanding the whole picture here but I see her willingness to accompany you to therapy and "agreeing to disagree" as great. I don't know what more you could ask of a believing born in with friends and family still in.
I am not sure of what you expected the therapist to say at her first session with your wife. Usually there is only time for the therapist to listen to the story and get a feel for the person and the situation.
My advice would be to hold to your decision to fade. At this point back off trying to convince her of TTATT. Offer her extra love, attention, and FUN. If and only IF she gives you a hard time about leaving remind her of her words to the therapist where she agreed to disagree. Then......
Accept her right to believe and ENJOY the rest of your life!