Certainly Dr. Sell - as a pope - had more influence due to his teaching the confirmation lessons. But I think the deep dependance and belief was due to Gretchen Fabrice who as a close friend practically never left the princess's side and shared her concerns in those very important teenage years.
Her parents had not been that religious neither had her brother. Except from Princess Karl there was nobody in the family with such an attitude.
The serious religious crisis Grand Duchess Alice went through, shows to me that she
was a religious person. Ella was a religious person, and the role of religion in Ernst Ludwig's life was important enough for him to have a private chapel built in the park of Schloss Wolfsgarten.
I wonder whether you aren't crediting Gretchen with too much influence. Alix commented on sermons and going to Church with her father or Miss Jackson even before Gretchen came into her life. Gretchen came when Alix was already 16 years old, that is, at an age when most people have formed views on religion, have developed an inclination towards religiosity - or a disinclination for religion. Alix' religiousness did not 'fade' once she was no longer influenced by Gretchen. This suggests to me that Alix' religiousness was something she had already in her. Gretchen and Dr Sell may have intensified some views and inclinations she already had and Dr Sell, as a theologian, most certainly could expand her knowledge, but I think it rather implausible that Gretchen instiled in Alix a "deep dependance and belief" that wasn't there yet. Most people do not become religious simply because a friend is a religious person; they don't start to 'depend on' religion due to influences of a friend/staff member.
As regards the questions Alix is said to have asked Father Yanishev, I think the type of questions makes it quite unlikely that this kind of thinking came from Gretchen.
Apart from the remarks from Gretchen to QV and from Toni Becker about Gretchen's influence, what specific details do you have on Gretchen's religious views and what evidence do you have of her influence on Alix' religious views?