You have received great advice. Go in with an open mind, do not overreact, try your best to not become emotional and do not make any decisions based on emotions. As hard as it is to hear things about our children, sometimes it is for the best and it surely won't be the last time. If the children in her current class are much more advanced emotionally or socially, it's worth considering moving her into the 3 class or she may "wither away" so to speak instead of blossoming into self confidence. Whatever you decide, I would make sure her academics do not suffer. Perhaps, the school could do a hybrid situation where she does specials with the 3 year old class and academics with the 4 year old class.
If you think she needs to be with the 4s, stand your ground and be the best advocate you can be. Is this public or private preschool? 4951