Keep in mind that Baldur's Gate is happening in a medieval setting, and while commoners might be a little loser with rules of etiquette than nobles, having sex before mariage at that time was not really accepted. Especially for people living in a monastery.Nonono! She did read those sex tomes Quitch! She tells this Anomen in TOB! No naive person would do that and certainly nobody would remained naive after that unless she was mentally retarded.
Sure, she might have read such novels, but I'm pretty sure she is not the kind of person to go have sex with the first cute random guard.
She was also probably reading them in secret, too. She also must have been feeling all rebel for reading those. Much like a teenager who go to a party without permission.
Edit: Also keep in mind that there was no birth control or real abortion back then. Most single female didn't really go around having sex for fun as they might do these days.