Mathilda's father
According to critics, Mathilda's father in the novel closely resembles Shelley's own father, William Godwin. As such, the representation of this character might be seen to symbolize her relationship with her father, and a manifestation of her grief after losing him.
Matihlda's physical health
Mathilda's physical illness is a key motif in the novel and is referred to multiple times. Her physical illness and demise represent her emotional suffering and the respective demise of her well-being. At the beginning of the novel she describes how she had been "withered" by past sufferings and tells us that she is "about to die."
Isolation
Isolation is another motif in this novel and is something Mathilda experiences from the very beginning. For example, she describes how she lives in a "lone cottage on a solitary, wide heath." She frequently references her isolation from the world, making her suffering seem more unbearable.
Telling her story
Another motif in this novel is Mathilda's desire to tell her story. This is her reason for recording her "tragic history," as she does not want her story to die with her. As such, the novel itself is her attempt to record her history, and reassure her loved ones she is leaving behind.
Suicide
Another motif in the text, Mathilda's life is impacted by suicide in a number of ways. Significantly, her father commits suicide after confessing to his incestuous love for her, and she then fakes her own suicide in order to escape.
