Calliope cuts her arms whenever she feels overwhelmed by strong emotions, abruptly changes from laughter to anger, and needs constant reassurance from others to feel any sense of self-worth. she is most likely to be diagnosed with disorder.

Borderline Personality Disorder

Explanation:

Borderline Personality Disorder is a disorder where the individual has frequent mood swings, unstable social and personal relationships and fickle emotional mood. Individuals with this disorder also have the need to feel any sense of self worth and are always overwhelmed with emotions.  The reason why a person develops the disorder can be linked to childhood experiences. Typically, people suffering from this disorder have had a traumatic childhood, or a situation that has imposed a major trauma into adulthood.

Calliope has many symptoms associated with this disorder, so we can conclude that she is probably suffering from Borderline Personality Disorder.