Not much the parents can do to be fair seeing these girls are both grown adults in the eyes of the law. You could be the best parent in the world but it won't automatically make your kid into an angel.
True, but it doesn't stop you from giving them some guidance...whatever their age.
I also think that if you bring them up to understand how to behave with some self-respect, they're less likely to make 'unwise' choices later in life.