Janeway would have no right to order Neelix to save another at the cost of his own life.
As long as Neelix travels aboard Voyager
, and serves in any kind of official function among the crew (head chef and ambassador), then Janeway has every right to give him orders just like she would do to any member of the crew. Neelix is not just a passenger - he has jobs to do. That gives Janeway the right to give orders to him.