Elena would probably be terrified at first. She's a human in a world full of powerful supernatural beings. Being kidnapped by Damon would mean she's in a very vulnerable position. She might initially try to fight back or escape, using any opportunity that presents itself.
Stefan would be extremely worried and angry. As Elena's other love interest, he has a deep connection with her. He would immediately start looking for her, using all his vampire skills and resources. He would probably suspect Damon right away, given their history of rivalry over Elena.
Elena would likely be angry. She has her own agency and doesn't like being controlled. If Stefan kidnapped her, she would fight back. She might use her knowledge of the supernatural world and her relationships with other characters to try to escape. For example, she could try to call out to Damon telepathically if they have some sort of connection in the story.
She could be terrified at first. After all, Klaus is a very powerful and dangerous vampire. But Elena is also a strong - willed character. So she might quickly gather her courage and start looking for ways to escape.
Elena would probably be terrified at first. She might try to fight back or escape immediately. After all, Kai has a reputation for being dangerous.
Elena might be heartbroken. She probably expected Damon to always be there for her, so his choice of Bonnie would come as a shock.
The Salvatore brothers, Stefan and Damon, are the most likely candidates. They both have a strong connection to Elena and would stop at nothing to rescue her. Stefan's sense of chivalry and Damon's fierce protectiveness would drive them to track down Katherine and get Elena back.
Elena would be devastated when Damon leaves her pregnant. She has always had a complex relationship with him, and this would be a huge blow. She might isolate herself at first, not wanting to share her situation with others. But as the pregnancy progresses, she would start to realize that she has to be strong for the baby. She would draw on her inner strength and the memories of the good times she had with Damon to find the courage to face the challenges ahead. She might also experience moments of hope, thinking that Damon could come back someday, but she would not let that hope consume her and would instead focus on building a life for herself and her child.
One possible motive could be Damon's possessiveness. In the 'The Vampire Diaries' universe, Damon has a complex relationship with Elena. He might kidnap her out of fear of losing her to someone else, like Stefan. Maybe he thinks that by taking her away, he can have her all to himself and make her see that he is the one she should be with.
Damon might initially be shocked and angry. He has always had feelings for Elena, and seeing Stefan marry both her and Caroline could make him feel betrayed. He might lash out and try to cause trouble for their relationship at first.
Their relationship becomes more serious and committed. With a baby on the way, they have to think about more than just themselves.