Going by interviews, she was a member of the coven and was in The Eighth Witch. However, I think it is speculative to say she was in 719 and 720, when we see the women there, and her actress is not one of them. We don't know how the curse would have effected Leota anyway. I personally speculate Leota is the dead woman that was sent a chocolate box. It all fits, the woman is dead (because Leota is a ghost), the woman ran a flower shop (because flowers are commonly used in funerals and wakes), and the woman's last name was the name of the funeral parlor on Lost (because, again, Leota is a ghost).