It was tweeted by someone (before the photos were released) that TMZ said their paparazzi had taken them.
If that is true, they might have staked out the area for awhile watching her come and go, then decided it was in fact her and started taking photos. Also, I can believe they were all taken on the same day even with the changes of clothes. If she is in a hotel going stir-crazy she might go out several times for walks. And she could change clothes in the course of a day.
The main problem I have is the close-up with the glasses where you can see her eyes, they do not look like Casey's normally bulging eyes. I don't really know how one would disguise that, but she could be squinting I suppose.
As far as jeans on a hot day, Casey might be one of those who is always cold. She wore or wrapped herself in sweaters in court. And even before she was incarcerated she wore a long-sleeved blue hoodie (yeah, that one!) even though it was July in Florida.
I sure would like to know how anyone found what appears to be Casey's twin if these photos are not her. Either the moles match exactly, or someone is a pretty good make-up artist.