*snipped*
IMHO, some of the return trips to G&C's post-6/16 were to pick-up clothes for the move in w/ Tony. In Tony's first statement to LE he referred to the 6/15 week very clearly as the time she brought most of her clothes over and moved into his place.
When Lee went to Tony's apartment late 7/15PM he picked up Casey's things and they were dumpted out @ G&C's. That is described in LE released docs in more detail, but, it doesn't give the impression there were many of Casey's clothes in what Lee brought back w/ him. Now, he may not have concerned himself w/ clothes that night...but, FWIW.
IMHO, during the transport in the Pontiac, Casey's clothes picked up enough decomp contamination that she could smell and she may have been worried about them having trace evidence on them, compelling her to dispose of them, hence, she needed new outfits. FWIW...it even appeared to me in the security cam pics that she's changed her outfit slightly between her ~10:30AM Target trip and her ~Noontime Target trip. She at least threw a shirt on over her dark shirt and changed sunglasses (in 1.5 hrs!!). Maybe she thought she was disguising herself so she wouldn't be recognized by the cashiers
Recall, Casey was a fan of the CSI show, and while it doesn't appear she was too careful about many other aspects of the crime...IMHO, the CSI shows tend to play up the whole found-a-piece-of-trace-evidence-on-perps-clothes/car/etc. and the case is solved...hence, she may have just tossed the 'smelly' stuff.
...not trying to drive this thread off into the decomp-smell ditch. Just wanted to comment to this observation that seems relevant to the Target purchases.