Patricia Dagorn, who faces a life sentence if found guilty, denies the charges.
Police believe Ms Dagorn met at least 20 men through a matchmaking agency between 2011 and 2012.
She allegedly asked most of them for money, or to name her in their wills.
Ms Dagorn, 57, is already serving a five-year prison term for fraud and theft.
After that trial, police re-opened an earlier investigation into the death of a man she had lived with, Michel Kneffel.
