I'm going to say more of what everyone else is saying -- if she is eating, peeing & pooping regularly, then you're fine. All cats are different, but I've noticed that the really bright, sensitive ones seem to take a little longer to get used to their new environment.

When I met my buddy Zorro at the Humane Society, he was friendly to me and sociable with his soon-to-be foster brother Einstein -- but once I got them home, Zorro hid in spots I didn't even realize existed (like, inside the frame of the recliner!) for the better part of a week. But it didn't last more than the first week or so, and he is now the most affectionate and well-adjusted guy you'd ever want to know.

My guess is that your new friend is probably more "freaked out" than actually depressed -- and it sounds like you are doing just exactly the right things to help her become acclimated to her new home. Bless you for getting her out of that store -- and now you'll need to tell us her name & post some photos!

BTW, welcome to Pet Talk -- looking forward to hearing more from you!

All the best,
Diana