From my Pokemon Anthroverse
As an Eevee, Solune wished to become an Espeon someday, however fate had other plans when a late night surprise Birthday party caused her to involuntarily evolve into an Umbreon. Due to this, she suffers severe emotional distress, mixed with the fear of her own dark powers, this can occasionally cause her to lose control of them leading her to damage those around her, further increasing her stress levels. She hopes to someday come to terms with her new form, and learn to control her powers.