I am certain that Jodi's murder of Travis was premeditated. I believe that was the sole purpose of her trip and that everything else that she did on the trip was to create her alibi.
Somehow, the murder trip took longer than Jodi expected it would. When she rented the car on 6/3/08, she planned to return it at 8AM on Fri 6/6. At some point, she changed the return date & time to Sat 6/7 at 9:30AM. She didn't actually return it until just after 1PM on 6/7. (
http://bit.ly/Vg36yn & http://bit.ly/WQKWnW).
Ryan expected her at ~10AM Wed 6/4. She called him saying that she was en route 6/3 between 9-10PM. In this call Jodi already knew that she was going to use the "I got lost" story to explain why she didn't arrive in UT when she said she was going to.
Using estimated time from Google maps, the trip from Pasadena to SLC* would have been ~9.75 hrs (684 mi). Adding a stop in Mesa, the quickest that Jodi could have gotten to SLC would have bee ~16.25 hrs (1071 mi).
When she first planned to have the car back by 8AM on Fri, she would have had to leave Ryan's by ~8PM on Thurs to make the 11.5 hr (767 mi).
The trip from Travis' to Ryan's would take ~10.75 hrs (684 mi). Jodi left Travis' shortly before 6PM Wed 6/4 and she arrived at Ryan's at 10AM Thurs. This gave Jodi ~5.25 hrs to nap and get rid of the knife, gun, her clothes, etc. This seems reasonable to me.
I think that she wasn't planning on being at Travis' house as long as she was there. The earliest that she could have gotten there, if she left Pasadena after calling Ryan (betw 9-10PM 6/3), is between 2:30 - 3:30AM 6/4 (388 mi, 5.5 hrs).
I now think that Jodi's original plan was to show up unannounced in the middle of the night, catch him sleeping, kill him and leave. I don't think she expected him to be up on his computer when she arrived and that she had to revise her plans at this point.
Looking at things this way, I no longer think Jodi ever had any thoughts other than killing Travis. I do not think that something happened in the bathroom that triggered her flipping out. The afternoon of sex was an improvisation that she had not anticipated. This makes Jodi's actions even more horrifying to me. She knew she was going to kill him the whole time they were napping, having sex & playing sex games.
*
I am substituting Salt Lake City for West Jordan because they are very close to each other