The Children of Wilton Chase by L.T. Meade

Ermengarde was sitting in her own room, and Marjorie was standing by her side. It was the day after Ermie's unexpected return home. She had spent a couple of hours with Susy, and Miss Nelson had given her a grave but kind welcome. Now the first day was over, the first night had gone by, and Ermengarde was sitting, resting her cheek upon her hand, by the open window of her pretty bedroom.

Marjorie was lolling against the window-ledge; her anxious eyes were fixed on Ermengarde, who was looking away from her, and whose pretty face wore a particularly sullen expression.