I think it sounds like the staff is giving you plenty of info, but you seem to processing it in a very personal way. Are you feeling defensive about the situation?
The staff told you your daughter was sick, and asked you to pick her up. She seemed fine when you picked her up, but shortly after came down with chicken pox. I would read this as--they noticed she was feeling unwell and they alerted you and I'd feel glad that they are paying attention.
Now the staff is telling you that she is cranky and out of sorts and having a hard time adjusting. Are they complaining or just letting you know how it's going? Are they telling you this and intimating that if she doesn't "get happy" she can't come back? Or are they just being honest about how her transition is going? I'd be even more unhappy if the staff were telling me that my DD was perfectly fine, and then I found out later that she was having a tough time.
I would ask the staff what she seems to enjoy there. Build that up at home and on the way there. Maybe try to set up a playdate with another mom/kid there--even if it's just stopping at the park for 15 mins after pick up.
Also, don't underestimate the chicken pox--getting sick like that can really derail her, make her more tired and miserable for a while. It also may be why she wasn't interested in her food during the day. I know the dr has said that she's clear to go back, but it might be the difference between being fine and feeling good. If she is still recovering, is there any way you could do shorter days there for a week so she gets some more nap time? You might find that in another week she's completely back to her old self, and happy again.
I would say, given you had a major sickness in the first couple of weeks, give her some more time to transition.