I would want to refer to the way that the other girls in the school react to Isabel's anouncement that she had something special to tell them at playtime. It is clear that the response to this and the sudden popularity that Isabel gains as a result is superficial and not based on any serious bonds of affection or friendship. This is of course something that Isabel herself manipulates to ensure her popularity, as the metaphors used suggest:
Playtime came and Isabel was surrounded. The girls of her class nearly fought to put their arms round her, to walk away with her, to beam flatteringly, to be her special friend. She held quite a court under the huge pine trees at the side of the playground. Nudging, giggling together, the little girls pressed up close.
The implied metaphor of "holding court" compares Isabel to some kind of medieval Queen surrounded by her ladies-in-waiting. The possession of the doll's house has given her power that she definitely exerts to gain herself popularity and importance among her social circle that is completely superficial and not at all based on mutual respect or liking.