Alessa is considered to be a misunderstood, tragic and tortured soul who only wanted empathy and love. The absence of paternal love may be the cause of her attachment to certain individuals such as Claudia Wolf and Lisa Garland, and Douglas Cartland and Harry Mason as Heather Mason. Selfless at heart, she cared about Cheryl Mason/Heather more than herself, wanting to spare them the hellish nightmare she endured at the hands of her mother, Dahlia Gillespie, and the Order. As Heather, she loved Harry Mason like a father due to the seven years of love and care he showered on her other half, Cheryl, and the fact that he helped end her torment and fulfilled her dearest wish of being accepted and loved.
Alessa also has a great deal of spite, which is shown most in Silent Hill: Origins, though this likely stems from the cruel and malicious treatment of her peers, her mother, and the god inside of her. Alessa is also known to be vindictive, scorned and dark-spirited. The Otherworld and Fog World are representations of Alessa's distorted perception of Silent Hill and her experiences there. In addition, Alessa is undoubtedly wrathful and easily lost sight of her pleasant visions of Paradise and the desire to be loved mainly due to the deity she was impregnated with, which continually fed her with unimaginable horrors and negative thoughts. However, it has been shown that Alessa has astounding amounts of willpower, demonstrated by resolutely enduring seven long years of pain, fear and madness and refusing to let herself be used.
Alessa kept a butterfly collection in her room, and had two dolls, one of which she named "Scarlett", and would often sleep with them in bed. Alessa drew monsters whenever she was alone. She loved playing card games with Claudia and would usually win. She loves literature, including Alice's Adventures in Wonderland, Oz, Mother Goose, Cinderella and The Lost World.