Nadia threatened Matt with hurting Tyler, he isn't as sure of how strong or powerful Tyler is so he's protecting him. Nadia is 500 years+ older than Ty and so much stronger. She has more experience, although Ty has venom so a bite would sort her out. But she is less likely than kat it kill someone she likes to keep it simple and only get physical or extreme when they really have to. She wanted to leave, she worried about the group suspecting and was shocked that kat even had to ask about how she should feel about saving Jeremy.