About Lugh and Nevan

Can someone explain why Lugh is sharing his secrets with Nevan? I was just reading the first chapters of Volume 5 and I was surprised that Lugh keeps showing Nevan his new inventions while knowing what she could do with that knowledge. All she did was promise that she wouldn't tell anyone about what she saw, but she could easily break that promise. I know that he threatened to kill her, but if he did after she revealed the information, he would be suspected of the act endangering himself and his house in the process. Am I missing something? Is there a logical explanation for this?