In my experience, if you think they are testing her, then they are waiting for her to "crack." To get really PO'd, tell them off, etc
I find that a direct appraoch is best. AS soon as she finds someone being rude, pull them aside privately and directly confront them ask, "DO you have a problem with my nursing care? I have observed when I do this, you _______." And describe the situation, ask for an explanation. Finish with, I don't come here to be friends, you don't have to like me, but it would be so much nicer if we could all get a long and act like a team. When you talk around me, it makes me feel like I am not a part of the team and I would like it to stop."
In other words it's time to grow some "cahunas", and don't bake for nasty people!!!!!!