The female would not lose any of her own rights, but as a married couple, assuming they want to live together, she would have to deal with the limitiations he has in terms of where he can live and the contact he is allowed with minor children. Additionally, the Father of the child may seek to remove the child from a situation where the child is having regular contact with a sex offender. If the Father pursues this, it may then be on the Mother to show why this is not a substantial change in circumstances. Before this woman marries a sex offender, I suggest she consults a local Family Law attorney to discuss her case in greater detail and to learn all of her rights and options. Good luck.