Star Wars Sexy Siren Billie Lourd is Halloween's winner for sexiest siren. Billie is not only in the previous Star Wars movie but also in the latest Star Wars film coming out late December.
However, Ms. Lourd is crowned Sexy Siren for her role on the series, American Horror Story. This season it is titled, AHS 1984.
I encourage you to watch the series and the previous 8 seasons. It will be worth it.