The correct answer to this open question is the following.
Amanda's moods seem to swing abruptly, and she often seems unable to control her impulses. She has had many sexual encounters and often complains of boredom, though she is seldom alone and often caught up in very intense, stormy relationships. Her friends are on edge around her because of her Jekyll-Hyde behavior. The psychological disorder that characterizes Amanda’s symptoms is Borderline Personality Disorder.
This is a mental illness that has a permanent pattern of changing moods, self-image, and the behavior of the person. That is why is compared with the characters Jekyll-Hyde behaviors.
It is very complicated to establish a normal or healthy relationship with these kinds of persons because of the impulsive actions, changing moods and problems that the disorder generates.