Pudding sounds scared. No big surprise, though, since cats are not normally big fans of change, especially a huge change like moving to a new apartment. (The bigger surprise is that your other two kitties have adjusted so quickly - that's a break, at least!)
It's usually best to let your cat get used to one room at a time, so keep her confined in a room with her water dish, toys and litter box. The reason for this is so she won't feel so overwhelmed. Moving can be traumatic for humans, but at least we understand what's going on. All a cat knows is that suddenly, her whole environment has changed and everything that was familiar is gone. Hopefully, making her "world" small at first by keeping her in one room, with familiar objects and smells will help her become acclimated to the new apartment. Leave a radio on low with some soft music, spend time with her in the room as often as possible and try to stick to her old routine as much as you can. You might also want to try a Feliway Comfort Zone plug-in. It's a diffuser of cat pheromones which calms cats in stressful situations. You should be able to find it at one of the large pet supply stores like Petco or Petsmart.
Good luck, hope Pudding will feel calmer soon.