One of the virtues could be her intelligence. In many villainess novels, the so - called villainess is often very smart. She is able to outwit those around her, even if her actions are sometimes misinterpreted as villainous. Another virtue might be her determination. Despite facing various difficulties and the negative perception of others, she continues to strive for her goals.
They are also presented in contrast to other characters. While the other characters may be weak - willed or overly dependent, the villainess with her virtues stands out. Her independence, for instance, becomes more obvious when compared to those who constantly seek help. Her loyalty, even if misplaced at first, makes her character more complex and interesting as it evolves throughout the story.
There could be her family members like her parents. They might play important roles in the story, either supporting or opposing her at different times.
A common trait is also being manipulative. The villainess will try to manipulate the situations and the people around her to get what she wants. She might manipulate the male leads by lying about the protagonist or creating misunderstandings between them to drive a wedge in their relationship.
It could be a very interesting novel. Maybe it's about a villainess who has reached an extremely high level in terms of her 'villainy'. She might have extraordinary powers or schemes at level 99. For example, she could be manipulating the entire kingdom's politics or be in a fierce rivalry with the protagonist.
I don't think it's a straightforward true story. Usually, such shows take liberties and combine various elements to make it more captivating. Maybe there are loose connections to reality, but it's not a pure retelling of actual events.
In manhwa, the isekai villainess is often characterized by her determination to change her fate and redeem herself. She might face various challenges and enemies along the way, using her wits and newfound abilities to overcome them.