Sabrina Lois Bartlett (born September 12, 1991) is an English actress. She is known for her television work, notably, playing Siena Rosso in the first series of Bridgerton (2020) and playing Mariette Larkin in The Larkins (2021). Sabrina Lois Bartlett (born September 12, 1991) is an English actress. She is known for her television work, notably, playing Siena Rosso in the first series of Bridgerton (2020) and playing Mariette Larkin in The Larkins (2021).