Borderline Personality Disorder (BPD): This diagnosis is considered the most likely due to the presence of emotional lability, manipulation, and suicidal ideation, which are hallmark symptoms of BPD. Although BPD is typically diagnosed in adults, the symptoms can manifest in adolescents, and early intervention is crucial.

Conduct Disorder: Characterized by a pattern of negative, hostile, and defiant behavior, which includes lying, stealing, and violation of rules. The presence of these behaviors, along with hypersexuality, makes conduct disorder a plausible diagnosis.
Oppositional Defiant Disorder (ODD): While ODD primarily involves a pattern of angry/irritable mood or argumentative/defiant behavior, some symptoms like lying and manipulation can overlap with those presented. However, the full spectrum of symptoms, especially hypersexuality and suicidal ideation, might not be fully explained by ODD alone.
Depressive Disorders: Suicidal ideation and emotional lability can be symptoms of depressive disorders. The manipulation, lying, stealing, and hypersexuality could be coping mechanisms or manifestations of the severity of the depression, especially in adolescents where symptom presentation can be varied.

Bipolar Disorder: Although less common in adolescents, bipolar disorder can present with mood swings (emotional lability), impulsivity (which could manifest as hypersexuality or stealing), and sometimes suicidal ideation. Missing this diagnosis could lead to inappropriate treatment and worsening of symptoms.
Trauma- and Stressor-Related Disorders (e.g., Post-Traumatic Stress Disorder - PTSD): A history of trauma could underlie many of the symptoms described, including suicidal ideation, emotional lability, and risky behaviors like hypersexuality. Failing to identify and address underlying trauma could hinder recovery and worsen prognosis.
Neurodevelopmental Disorders (e.g., ADHD): Impulsivity in ADHD could contribute to stealing, lying, and hypersexuality. While ADHD itself might not fully explain all symptoms, comorbidity with other disorders is common, and missing ADHD could impact treatment efficacy.

Factitious Disorder: Characterized by the intentional production or feigning of physical or psychological symptoms, which could potentially include suicidal ideation and other described behaviors, primarily for attention and sympathy. This diagnosis is less likely but should be considered if the behaviors seem to be primarily driven by a desire for attention.
Neurological Disorders (e.g., Frontotemporal Dementia, though extremely rare in adolescents): Certain neurological conditions can lead to significant changes in behavior, including impulsivity and hypersexuality. While exceedingly rare in a 14-year-old, any sudden onset of such a broad range of symptoms without a clear psychological explanation might warrant a neurological evaluation.