Maybe he wants to pass on some important message. Since he's dead, perhaps he has some unfinished business and by telling the girl his story, he hopes she can do something about it.
It could be that he was wrongly accused or met with some great injustice in his life or afterlife. He kidnaps the girl just to have someone to listen to his side of the story so that the truth can be known.
The girl may initially struggle and try to escape. However, if the dead cowboy doesn't seem immediately threatening, she might gradually calm down and listen to his story, out of a mix of fear and intrigue.
One possible motive could be to use Hermione as a bargaining chip. Maybe Narcissa wants to exchange her for something important to the Death Eaters, like information or the release of a captured Death Eater. In the wizarding world of 'Harry Potter', such power - play is not uncommon among the dark forces.
The masked man might kidnap Lucas for ransom. Maybe Lucas comes from a wealthy family in the fanfiction world, and the kidnapper sees an opportunity to get a large sum of money.
One possible motive could be to gain an advantage over Harry Potter. Hermione is Harry's closest friend and a very intelligent witch. By kidnapping her, Draco might think he can use her as a bargaining chip to make Harry do something or to get information from her that could be useful to the Death Eaters. Another reason could be jealousy. Draco has always been in competition with the Gryffindors, and Hermione's intelligence and skills might make him envious to the point of doing something drastic like kidnapping.
One possible motive could be that Lex Luthor sees Superboy as a threat. Since Superboy has super - powers, Lex might want to study him or find a way to control him. Maybe he plans to use Superboy's powers for his own evil schemes. Another reason could be jealousy. Superboy is often seen as a hero, and Lex Luthor, being a villain, can't stand someone having so much power and adoration.
Another motive could be that Uncle Phil has some sort of secret that he thinks Jamie has discovered. He might be worried that Jamie will expose this secret, so he kidnaps him to keep him quiet. This secret could be something related to the family's past, like a hidden treasure or a dark family secret that Uncle Phil wants to keep buried.
The Salvatores, Damon and Stefan, are likely candidates. They have always been protective of Elena and would do anything to save her. They could use their vampire skills and knowledge of Kol's weaknesses to stage a rescue.
Mario would be a likely candidate. He's always been the hero in the Mushroom Kingdom and has a lot of experience dealing with villains like Tatanga. He could use his jumping skills and power - ups to make his way to Tatanga's lair and rescue Rosalina.
The 'her' could refer to the person who first had the thought. Maybe it was a female researcher, an artist, or an activist who came up with an idea that became the 'thought of the year'.
It could be a terrifying situation. Maybe the kidnappers have some evil plan or they are driven by some crazy motive.