I'm thinking that she altered the EXIF data on some old sex pics, then put them on a memory card she had with her (she knew prior to the trip what kind of camera Travis had purchased), then put that memory card into the camera, before taking the shower/murder pics.
She kills him, then she dyes her hair brown so that when Ryan Burns sees her, it matches the sex photos. It also disguises her from how the rental car guy and any surveillance cameras saw her.
She knew she'd be busted. She just wanted people to think that Travis just HAD TO HAVE HER one last time before he died.
I just cannot bring myself to believe he had sex with her 8 days after sending her that text that said she was the worst person he ever met, and a complete psychopath. It makes NO sense.