Many sativa strains have a genetic propencity to produce seeds even when it's not pollenated. It's not that big of a deal but it will impact the quality of the bud. However, From what you said it sounds like mellow is right and you got a hermie. Do your self and the species a favor and smoke what you can of the bitch and kill it and the seeds. It's up to you to plant the seeds, but If I were you I'd just toss em and go with good seeds. In the end it's your choice.