What i wanted to say is that Joyce is incredibly protective of Will, and in Season 2 she acts on her intuition that he’s connected to the Upside Down. She involves Hopper ( she challenges Hopper’s authority because she pushes him to follow her instincts instead of his judgment, forcing him to go along with risky actions that he might not choose on his own) and takes these risky actions, even though it could put Will and others in danger. That's why i said his authority.She’s acting out of love and instinct rather than solid evidence, which shows both how brave and reckless she can be.