IMHO if you have even the smallest doubt I would remove the child from the daycare and either move them to another, or bring them home.

With my first son we ignored some of the doubt, thinking we were being overprotective first-time parents. Once we made the decision to move him to a new daycare, the changes in my son were immediate. He was socializing with kids, and learning much more rapidly than before, and in general much of the behavioural problems we were having disappeared.

Thanks for clarifying - if taking her out of nursery is what you feel you should do then do it, your the only one that knows what's best for your own child.