you research coding so on night 10 when you find a usb in the vip room you decrypt it and that will help you get her name if you have missing persons at 900 then research it to 1000 and it will give you her name
Viewing post in A Fortnight at Frenni Fazclaire's comments
but did you decrypt the usb? you find it on night 10 and you need 1000 on coding to decrypt it then if you research missing persons to 1000 then it will work you can free Marie on night 12 when you go and talk with Frenni, Maire will try to attack you and you can say Marie's name and i think even night 14 you can free her at the start of the night