A lot of you have been coming up with fake reasons why mikaela left. Some of you are even wanting her back for the fourth for some human story. I posted this is another thread, and I think THIS should be why she left: The reason why she left Sam was because she was scared. She was scared after she had seen him almost die in Egypt. In fact, they both almost died. After that, she wanted him to give up saving the world with the autobots. He just wouldn't do it. He didn't want to give up saving the world with the autobots. He didn't want to give it up for himself or even for her. She didn't understand it, and she really wanted him to give it up once and for all. He simply refused. She was scared and was living in fear that she would witness his death in the future. So, she just got up and abandoned him. she didnt want to see that. So it was better for her to leave no matter how much it hurt rather than witness his death, which would hurt 10x more. She changed her phone number, she moved, she didn't want to speak to him again, cause it would hurt too much. SO WHAT ARE YOUR THEORIES?