Lucy is constantly going back and forth from looking healthy to looking sickly pale. What is happening to her? How do we know this?

A) She is suffering from anemia caused by excessive blood loss. This is evident from her fluctuating energy levels and physical appearance.
B) She is being affected by Dracula's nocturnal visits, leading to a gradual loss of vitality. This is indicated by her changing complexion and behavior.
C) She is undergoing a transformation into a vampire due to Dracula's bite, resulting in her alternating between life and death. This is suggested by her changing physical attributes and behavior.
D) She is experiencing psychological distress, leading to a fluctuating state of mind and physical well-being. This is implied through her inconsistent behavior and emotional instability.