Avram – I would assume that she feels that speaking to someone when they happen to pass by in the hallway is different than knocking on his door late at night.
She does mention that if the situation were reversed, she wouldn’t want him to knock on her door. So she was acting towards him the way she would want him to act to her.
I actually just noticed now that she wrote that. I think that is an important point for anyone who may have judged LB unfavorably to keep in mind. She was not “being Frum at someone else’s expense” but rather, it seems that she was considering what she thought he would prefer her to do (and even if she was wrong, it was just a mistake and she had no way of knowing what he would want – she could only go by what she would want in a similar situation.)