She was attracted to him deeply

This was the first time Janna met someone so manly. His dark skin made his look ibtensely hot. 

Despite the arrogant attitude, he was kind to his men, attribute that no king or royal blood alike didn't have. As far as she had known at least. 

She had special access inside the palace even if the king didn't recognize her as his daughter. That's why she heard them talking about the syrange prince from far away land.

She wished she is his wife, she knew Novalian men had many wives, that's why she was so determines to take his attention away from all of his wives.

That's why she used the forbidden spell on him. The spell was taought by her adoptive mother. That woman knew all witchcraft secrets in the world but she suddenly disappeared like the magic that she did.

Janna didn't learn all of it but learned enough to seduce the person that she liked.