Bonnie is perfectly fine. Absolutely normal. As if she never left. Back in the old routine........well, you get the picture.
As it stands now, she will be a long term foster. I will not prevent her from finding that perfect home, but I will not allow her to go into their shelter building, not as long as she can have MY home. Don't get me wrong, their shelter building is nice, such as it is, but it is not a home where people give personal attention to each individual cat. It is divided into rooms, only a couple cages for newcomers or sickies, but it is full and they do not need another body in there right now.
I am encouraged by stories of other cats who had this same thing happen in their first potential home only to go on to find a different home where they were comfortable and stable. So it will come along, she just needed to stay here a bit longer.