Yes children should be perfectly capable of 'self initiative and solitary play' by that age for sure ~ it could be that when she was home someone always 'entertained her' so she does not know HOW to play and will need some promoting or she could be overwhelmed by all the choices in your playroom so is just standing and watching the others cause she is not comfortable yet to 'choose' so to speak ~ sometimes with children like that who tend to just stand and watch and are slow to enter play if they are taking a REALLY long time and seem upset about getting into the play than I will let them know the expectation and offer them two choices 'it is time to play now ~ do you want to play with blocks over there with Johnny or go explore the kitchen centre with Sally' and help get them started on entering play and than I back off and let them do it on their own ... would that work with her to partner her up with a 'child' to play with initially until she figures out she can play on her own as well?