I don't know who that smart poster is either, but I do recall hearing that theory several times. There had to have been a precipitant event in my mind as well.
I've always been of the opinion that it must have been something that struck to close to the carefully-constructed image Jodi was trying to present. Narcissists can go into a rage, particularly when their artificial "self" comes under challenge or someone threatens to expose the facade as a lie. They will sometimes see that threat in life or death terms, given that they identify their physical existence with the false persona they project to others.
Travis might very well have threatened to reveal something about her to others involving theft of money, perhaps of property like the ring, or something else that we know nothing about and never will unless she admits it (and at this point, I won't believe anything she says without corroboration.) I could see that sending her into a blind narcissistic rage. She may well have been seething for some time, but those last phone calls on May 26th were the coup-de-gras in my view. He might have discovered something important missing -- it could have been the ring. He might have confronted her about it that night and told her they were through.
One thing though -- I don't think he knew she was coming. If the precipitant cause was the ring, she was certainly devious enough to consider bringing it with her and putting it somewhere in the house, so that in the event Travis had actually "outed" her as a thief, she would be able to point to its eventual discovery and say, "see, I didn't take it." That might have been another support for her "alibi" in her own mind -- she knew very well that his friends were going to point the finger straight at her, so every little bit of evidence she could use to dispel their stories about her would have been useful to her.
I can't see that she would have gone to all of the trouble of the rental car, gas cans, hair dye, no cell records in AZ, just to hope that Travis wouldn't mention to someone that she was coming. She could not have taken that chance given what she had in mind. She thought she would get away with killing him.
:cow: