She can't let anybody know. Ever. If they knew... hell, if they even thought that...

No. If she doesn't think it, it's not true. Because it would be so far beyond wrong. He's everything she's against, and for good reason. He kills people, for godsake! His calling in life is to make sure people die. He may not pull the trigger, or be the one who is driving the car that runs someone over but he may as well be. He knows they're going to die, and he does everything he can to make sure they do. He goes out of his way to stop her from saving people.

So if she doesn't think, doesn't let herself feel, then maybe it's not really happing. Maybe she isn't really necking with him against a wall in the same room of a girl who she failed to save.

Maybe is she doesn't let herself feel it, she won't be in love with him.