Complex sentence: The night of the ball begins, and Ella tries to join her step family on the way out, but Lady Tremaine, claiming that her mere presence will disgrace them, leads her daughters into ripping up the dress before leaving without her.
Split into simpler sentences: The night of the ball begins, and Ella tries to join her stepfamily on the way out. However, Lady Tremaine, claiming that her mere presence will disgrace them, leads her daughters into ripping up the dress before leaving without her.