Laz couldn't be using his sense perception every moment of every day. He would get a splitting headache as he had found out the hard way before. The feeling was like constantly being on edge for a long period of time. It basically lead to being exhausted and in pain. It just wasn't needed or worth it.
That said, he also knew that he had felt vibes from this girl before when he came into contact with her so he wasn't able to figure out why he no longer felt it. After her attack the last time, he knew she was like him, strange. But now she seemed to give off the feeling of a perfectly normal person with no abilities at all. This was the real reason why he was surprised.
Malene just continued to lean on the wall and look at him. He had to admit that she was a budding beauty, even if she annoyed the hell out of him during their last encounter. He couldn't figure out how he had gotten cut, no matter how he looked at it.