After thinking the "shooting first" made more sense I have done a complete turnaround. Jodi planned every minute detail right down to turning the license plates. So the murder was planned to a T. I believe she planned on BOTH stabbing and shooting Travis to make it look like there were 2 killers. She planned on stabbing first (why would you stab if your gunshot already killed him) and then shooting him. I wouldnt be surprised that she planned on stabbing right handed and fire the gun left-handed or visa versa to aid in the 2 killer story. I think she planned on doing both in the shower - first, sitting in there would make him more vunerable and 2nd it would contain the blood.
What went wrong was that after being stabbed, Travis was able to get up and out of the shower before she could shoot him...therefore she had to stop him by repeatingly stab and ultimately slashing his throat...since her original plan was to shoot in shower, she dragged him back and put him in plus the reason for attempted clean up (trying to return to her master plan).
I welcome alternate theories or reasons why my theory doesnt make sense!