I agree JA was facing all the above, however with her personality disorder which ever one she has, (I think she has probably more than one), but I believe it was more than those issues you mentioned. In her twisted mind she has the confidence that she could lie her way out of anything, and from her behaviour I think she still thinks that. So I think it was more than all the factors you mentioned.. that set into motion the murder. I think Travis calling her a sociopath was the final check mark she needed to follow through with her plan - which I think she had set in motion long before she actually did it. The calling her out....that was something she could not tolerate. (imho)
So do you think the inital "trigger" (sorry) was the romantic rejection/devastation she felt? And the rest of the pieces were the final nails in his coffin (stop it!)? I'm really not trying to be funny because this was a horrific event, but those phrases just seemed to fit here.