Her good looks are the reason why the emperor took another man's wife as his mistress. Her lifestyle also helped her look young for her age, as she doesn't have to do manual work or stay out under the elements. But the biggest reason is, this is a manhwa, it's not real life, nothing needs to make sense, so yes she is the mother of two adult children and she still looks so young and beautiful despite her hideous personality.
Her good looks are the reason why the emperor took another man's wife as his mistress. Her lifestyle also helped her look young for her age, as she doesn't have to do manual work or stay out under the elements. But the biggest reason is, this is a manhwa, it's not real life, nothing needs to make sense, so yes she is the mother of two adult children and she still looks so young and beautiful despite her hideous personality.