I have a test where I am given the following article, what is an answer for the question: Whose sister dies from a heart attack? ?

Upon receiving a key from her Uncle Max, Cabella travels to Italy where she discovers the key is related to a house named Cabella near a village. While traveling she stops near a waterfall to swim and loses the key, but a mysterious man returns the key. She then travels to the village, finds the house, and uses the key to open it.
The next day she goes to the market where the mysterious man works and learns from his cousin Maria that his name is Leo and he is deaf and mute. Maria and Cabella become friends and Maria introduces her sisters Sophia and Giulia. Later that evening Maria tells Cabella that she has a crush on Lord Jai, a rich man from India that attended a boarding school. That night, Cabella has a conversation with a spirit named Angelo and has strange dreams about her mother. 
The next morning, Cabella finds a basket with goods such as eggs and apples sent by Leo. Maria then takes Cabella to her sister Ambrosia's funeral because she died from a heart attack. That night Angelo visits her and confesses that she must go to the cemetery to learn more information. At the cemetery, she meets Senior Bronzini, who, according to rumors, had a relationship with a nun when he was younger. Cabella decides to leave flowers for Chiara, a woman buried next to Ambrosia who has no flowers.

Maria