I'm surprised no one has brought up the possibility of human trafficking yet. This is an industrial area near highways (i think) and that's a breeding ground for grabbing people and taking off. I wonder if police have looked into cars caught on CCTV yet to see if they're linked to other crimes or registered offenders.
As for the posture, I agree with
@Dre- A lot of GNC, genderqueer, trans, and other visibly LGBTQ folks tend to walk with guarded, "masculinized" posture, especially in non-confirming or unsafe spaces. I know I myself walk like she was all the time (I'm very visibly gay).
And on the topic of the video, which I'm SO glad we have now- Maybe the purpose she was walking with was one of more "I want to get some stretching in". Maybe she had a walking path thought out in her head and planned to just do a lap of the lot. And for eating on her breaks, I rarely eat on my lunch breaks. I know that might seem odd but plenty of people just don't feel like it.
@Taylorbgilbert is it possible that your sister had some sort of eating problems or a poor relationship with food? if so, this may explain a theory of her going for a walk or skipping meals. I also agree with
@Gobstopper that it could be a matter of feeding others and saving money for them- god knows that a lot of young "Giver" types will sacrifice their own nutritional needs for dependents.
What really gets be about this case is quite how many possibilities there are and how many puzzle peices are missing. I wish we could find that man she crossed paths with (I'm almost positive he was an employee) and ask him about that night.
@Taylorbgilbert I hope you're family gets some answers- and Brianna- back soon!