I respectfully disagree with you. After all has been said and exposed, it's obvious to me that Jodi decided to become a Mormon for the very specific purpose of trying to hook TA for life. She used sex to keep him interested and to manipulate him because it was all she had. Jodi knows how she is expected to behave but she has no substance as a human being. Undoubtedly she has self-loathing but I don't think for a second that she is or was interested in redemption.
Oh, you're right, it's not redemption at all. It's destruction, annihilation, obliteration. I see it as a completely selfish act, 1) because she took the life of another rather than face her own ineptitude as a human being, and 2) because she allowed her mental issues, her personality and her overblown sense of self-importance to grow completely out of control. Most of us have the training to be able to put our problems in perspective and to submit to getting help if we need it. Not JA.
Jodi became interested in Mormonism because of it being a component in PPL; not as a matter of faith but as a matter of fortune. Those Mormon boys were coming over to where she lived with Darryl, (which is when she told him "no more sex.") I'm sure the lure of the LDS church for Jodi was the young male missionaries so eager to have a chat, and later she used it as a way to get closer to TA.
JMO it's simplistic to say that JA used sex, because TA used the sex too; used it as a part of his secret life, as an outlet, as an escape into fantasy, and yes, to control JA. Personally, I don't see anything they did sexually as being pertinent whatsoever, since it ostensibly was mutual and consenting. Where they got into trouble was in their attitude about the sexual activity - the difference being that TA was taking steps to extricate himself from the sex and JA was taking steps to enmesh herself more deeply.
The reason why JA turned her cell phone off on the long drive to Mesa? Not to avoid pinging cell towers, but to avoid any voice, any sound, any suggestion that she turn away from her intended purpose.