Isabella was the daughter of Guido and aliases of a human female from Venice.

Isabella was sent to Rosanna Calvierri's school in Venice, unaware she was to become a bride for Rosanna's sons. She was put through the transformation, but was not as far as the girls around her.

When Amy Pond went undercover to open the trap door for the Eleventh Doctor, Rory Williams and Guido in 1580, she met Isabella. When the Doctor and his friends were trapped, Isabella showed them the way out but couldn't leave because the sun burnt her skin - despite not being a full Saturnynian yet. Rosanna deemed her a traitor, and punished her by pushing her into the canal. Thinking she wished to drown her, Isabella swam. Seconds later, however, she was pulled under by Rosanna's children, and was devoured.

The Doctor talked to Rosanna of Isabella's death. He was angered that Rosanna did not know her name. (TV: The Vampires of Venice)