We already knew that Leora was a nervous type as she would not sleep without the light on or when Paul was in the room.
This is just another example of her jumpiness, that's all. It's nothing to do with being smart.
Smart people can be afraid of spiders and mice, so it's not an intellect thing, it's more instinct and conditioning.
Some people jump when you walk into the room without making a sound, 'you scared me to death' while others just say 'hi'
I don't think it makes her stupid in the least. Just human.