Sorry, Sisters Pocket and Geevee, but after twirling that kaleidescope until I was dizzy, I'm as sure as it's possible to be (given the many unfillable holes in the evidence) that the sex photos were taken that day.
I'm equally sure she lied about what happened that day, beginning to end. It's even possible, IMO, that TA did worry she might surprise him on her way to Utah, and locked every single door, knowing she knew how to sneak in, undetected, and that one reason why she was so behind schedule and the sex photos weren't taken until 1:30ish is that she couldn't get in, and had to wait until TA woke up and answered the door.
Maybe by that point he was beginning to clean, and she interrupted him from that, which is why she didn't see him taking off his watch and ring, or notice that he had. I still think she must have been in the study with TA when Zach returned. More delay.
About the photo CD's. If she did bring CD's of their trips, IMO it was part of a plan to play act a nostalgic, all is forgiven parting. LOL that she overlooked bringing the CD's helped prove premeditation.
If she didn't bring the CD's, she perhaps lied to fill a time gap in her story line, but more importantly, IMO, she thought that lie reinforced her big lie about TA still having plans to travel with HER. (Take that, Mimi!). And....her lie about bringing them helped prove premeditation, lol either way.
Omitting talking about sex that day in both her letter and manifesto, and her absurd insistence that she wanted to take "tasteful" photos of TA in the shower? Perhaps simply because the was already trying hard to portray herself as the more spiritual of the two, and Travis as the one sexually obsessed, and with her.
Travis made her take those photos, doncha know?