A couple things I noticed:
I think possibly we misread the "block away" part - now that I'm rereading it, it appears that they dropped her off at work, a block away (from their home?) and not a block away from work. Shellz, was labor ready a block from their home? Would that make sense?
Also, I read that she was dropped off at 10am - that seems a little odd as well, unless she knew where she was going that day and with who. Things may have changed since I was working for a firm that used Labor Ready, but from what I remember, Labor Ready worked very similar to the day labor found outside Home Depot, but legally. It was pretty much first come first serve if you didn't already have an assignment lined up. Most people would arrive around 6am or even earlier to get a better chance of getting an assignment. This was the early to mid 90's, pre-internet, so the process may have changed by the time she went missing, but just something I thought worth mentioning.
If she was dropped off at 10am, she more than likely had been scheduled at that time for a specific assignment that she knew about.