Why were fern's parents worried about her?

Fern's parents were worried about her because she was showing signs of distress and emotional turmoil, particularly regarding her relationship with her pet pig, Wilbur. They noticed that she was deeply affected by the idea of losing him, as she felt a strong sense of responsibility for his well-being. This concern for her emotional state led them to question whether she was overly attached and if it was healthy for her development. Ultimately, their worry stemmed from a desire to ensure Fern was happy and well-adjusted.