In some fanfictions where Draco kidnaps Hermione, his motivation could be related to family pride. The Malfoy family has long - held grudges against the 'Muggle - born' status that Hermione represents in the wizarding world. He might see kidnapping her as a way to assert the superiority of pure - blood wizards. Another possible motivation could be jealousy. Draco may be jealous of Hermione's intelligence and close relationships with Harry and Ron. By kidnapping her, he could try to break those bonds and prove himself more powerful.
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.
A common plot twist is that Hermione actually has a hidden power or ability that she reveals during her captivity. For example, she might be able to use a type of magic that Draco and his associates didn't expect, which gives her an upper hand in the situation. This could lead to a change in their relationship dynamic, from captor - captive to something more like equals.
She could be defiant at first. Hermione is a strong - willed character, so she might immediately start trying to escape or use her magic against Draco. She could also try to reason with him, asking him why he's doing this and trying to appeal to his better nature.
One possibility is that it could be a dark and twisted take on the relationship between Draco and Hermione. Maybe in this fanfiction, Draco has some ulterior motives that lead him to this extreme act. It could explore themes of power and control as he forces Hermione into a situation she doesn't want. However, it also might lead to a redemption arc for Draco as Hermione tries to change his ways.
She would most likely be furious. Hermione is a smart and independent character. She would immediately start planning her escape. She might use her knowledge of magic to try and outwit Draco.
One common theme is redemption. Draco often starts as a villain in the act of kidnapping but through his interactions with Hermione, he begins to change and seek redemption. For instance, he may realize the error of his ways in following the pure - blood ideology.
In many fanfictions, Hermione will try to outwit Draco while she's kidnapped. She might use her vast knowledge of magic to escape or at least send some sort of signal to her friends. Meanwhile, Draco could start to have second thoughts about what he's done. He might realize that kidnapping Hermione was a wrong move, especially if he has some underlying feelings for her. This could lead to a change in his actions, and he may even start to protect her from other threats that might come his way, like other Death Eaters who want to harm Hermione for her connection to Harry.
Perhaps a plot twist could be that Draco is under the influence of a dark spell when he kidnaps Hermione, and as she tries to break the spell, she uncovers a conspiracy within the wizarding world. Or it could be that the kidnapping is a ruse set up by Hermione herself to infiltrate the Slytherin group, but Draco doesn't know it and things spiral out of control.
Dumbledore could play a crucial role in her rescue. He has great wisdom and powerful magic. He might sense that Hermione is in danger through his magical connections. Then he could send some of the more skilled members of the Order of the Phoenix, like Sirius or Lupin, to find and rescue her. They would be able to use their combat skills and magic to overpower Rabastian.