My ex-girlfriends nurse is taking the wrong course of action for her treatment so I think I'm going to have to become very defensive about this.
Are you a nurse? Did you study nursing?
It's pissing me off because I think her recommendations are bad.
You're allowed to be angry if someone you care about, such as an ex-girlfriend, is being treated poorly. However, the nurse is a medical professional and most likely knows better about how to take care of your ex. You should calm down and let them handle the situation even though you're most likely feeling very helpless right now.
I'm really angry because I believe the nurse is wrong.
Everyone feels that way until they put themselves in a nurses shoes. It's a stressful profession and family always think they are right and will only learn if something will happen for going against the directives.