Just my two cents, based on having been married to her male equivalent, but here goes.
Psychopaths do not have any real feelings for the people in their lives. They only serve to fulfill a need for them at the time. Psychopaths also have many different people in their lives that they maintain different personas with. That is the main reason why they do not allow their families and friends to know one another. (Jodi's family never even saw a picture of Travis till after he died.) They are maintaining different stories with each set of people they know. That is one of the reasons they have lives in several different cities or states in this case. They can create whatever persona they want without fear of others knowing.
A psychopaths worst fear is to be exposed. If everyone they know gets together and begins to exchange stories, their scam is up. Travis had IMO found out something about her that she feared he was going to expose. I believe she figured this out in the time frame of the text that said she "was the worst thing that ever happened to me."
Psychopaths are masters at being whoever they need to be to get what they want. I think once she decided she was going to kill him she spent the next few days playing on his sympathy for her. She wormed her way back in enough to get him to let her in to his home. She toyed with him all day like a cat toys with a mouse. Why???... Because it was fun for her. She did what she had to do to make him feel safe with her around, the whole time knowing that she was going to kill him. I don't think he knew what was coming till that last picture in the shower of his face close up.
Most of the men in her live up until Travis seem to have been less than decent people, therefore, they may have not been able to have the impact in exposing her that Travis would have had.
Jodi realized that her welcome was over in Arizona and that is why she left. Had Travis of not threatened to expose whatever it was I believe he would still be alive today. Sadly I believe that Travis actually cared for her at some point and was compelled by his big heart to keep on trying to get her to be a better person. I don't believe it was some sort of sex addiction that kept him coming back. (Honestly I don't understand all the fixation on sex, he was a 20 something year old man, after all. I don't know any 20 something year old man that does not think about sex at least 10 times a day). But whatever he discovered in late May was the last straw for him.
My guess is that Jodi had been getting away with petty crime for all of her life. Her ability to manipulate people into thinking that she was someone other than who she was emboldened her to believe that she could have gotten away with this. IMO IF the camera had not been found she quite possibly would have gotten away with it.
Now that her first and second stories are able to be proven lies, she had to come up with one more. It was her only chance. Her ability to sit there and watch Travis's family be harassed and hurt by her accusations, and continue to be snarky and obnoxious shows that she never cared about Travis at all. She is one evil person, and she should be used to teach young men and women for that matter that there is true evil in this world and you need to be careful not to get sucked into their evil web.