Good for her, if this really is about her convictions.
In SOME cases, people are virgins or chaste because they have hangups or low drives. The person marrying them think they are marrying someone who has been of strong character, only to find out that it is easy for someone not to steal bread if they are never hungry.
Not every person who fornicates feels bad about it, or gets an STD, or has an unplanned pregnancy, and we should not say they will, or we look like fools. But it IS correct that much of our social ills will be reduced (STD rates, abortion, out-of-wedlock births) if more people saved sex for marriage.