They make her act that way--Mr.Tappan makes her.

Our grandfather didn't want us to have friends." "I'll tell you what," said Scott impatiently, "when I'm old enough, I'll have other boys to play with whether Kathleen and--and that Thing--likes it or not." The Thing was the Half Moon Trust Company.
Geraldine glanced back at the portrait over the divan: "Do you know," she ventured, "that I believe mother would have let us have fun." "I'll bet father would, too," said Scott.

"Sometimes I feel like kicking over everything in the house." "So do I and I generally do it," observed Geraldine, lifting a slim, graceful leg and sending a sofa-cushion flying.
When they had kicked all the cushions from the sofas and divans, Scott suggested that they go out and help Schmitt, the gardener, who, at that moment, came into view on the lawn, followed by Olsen wheeling a barrowful of seedlings in wooden trays.
So the children descended to the main hall and marched through it, defying Lang, the second man, refusing hats and overshoes; and presently were digging blissfully in a flower-bed under the delighted directions of Schmitt.
"What are these things, anyway ?" demanded Scott, ramming down the moist earth around a fragile rootlet from which trailed a green leaf or two.
"Dot vas a verpena, sir," explained the old gardener.

"Now you shall vatch him grow." The boy remained squatting for several minutes, staring hard at the seedling.
"I can't see it grow," he said to his sister, "and I'm not going to sit here all day waiting.

Come on!" And he gave her a fraternal slap.
Geraldine wiped her hands on her knickerbockers and started after him; and away they raced around the house, past the fountains, under trees by the coach-house, across paths and lawns and flower-beds, tearing about like a pair of demented kittens.