It is strange, even though TA has referred to her as such, even the Hughes (whom they spent a lot of time with initially, and TA remained in contact with - despite killer's attempts to sabotage his friendship with them), have stated that there is no evidence that TA and JA were 'in a relationship.'
They stated that a few times in their book. Yet, TA never corrected her when she referred to herself as his girlfriend in the audio we've heard so... I believe Travis WOULD have, for sure, if he felt uncomfortable with her calling herself that and the context was pretty clear. "I wasn't your girlfriend then."
I DO believe, their relationship was BS, all lies, how is that a real relationship? It is one of victim/predator, that's all. No REAL relationship, any sincerity or bf/gf type atmosphere WAS short, in my personal opinion. There is evidence for that too. Hell, I'd buy he'd have only called her gf for a week, at best, their only functional week together (maybe even just a short weekend of bf/gf recognition), else, they were fighting all the time! Evidence of this, and JA stated this herself in her own diary so..
I do NOT believe they were truly on a bf/gf level, however, not just due to pathological sabotage (one after another), but because if you are fighting all the time, that is evidence you are not even on the same page, they were simply DATING. He called her his gf only due to his uncomfortability at some point with the nature of their exclusivity. She made him jealous, so that was provoked too perhaps... just to call her his gf, that is.
I mean, at that point, she had managed to aggravate him into arguments with others, he'd have to defend 'poor Jodi,' and everyone would wonder why he was with her. She greatly manipulated their so-called bf/gf 'relationship.' False relationship, that's what I'd call it, JMO.