Seeing the light inside the cow frightened her. There is no simple explanation for this. It is just that she had never thought about cows in this way. You must admit that a dramatically different direction like this can be somewhat daunting for a mind unused to time travel.
He didn't think about it in that way, though. For him, the light inside the cow was just another light inside another cow. He always looked at the bright side, the light side and found that it was mostly the inside. He couldn't quite understand why it frightened her. He didn't know about the darkness. He dreamt about it once, but inside he had the light. Even in dark dreams. And at night. Maybe that is why she loved him. She had always been adventurous, in spite of the fear. Attracted to the dark. The night. But for this, she needed light.