You set limits. Doesn't sound like you did anything wrong. I guess I'm confused at what "B's" side of the story is that is causing you to be bothered by your NM on your day off. Is she accusing you of abuse? Threats? Being a good psych nurse and actually setting limits? I think I'd be having a talk with the NM about appropriate admission criteria for your psych unit. The dying fellow and his probable inapproriate placement there sounds like the bigger issue, but I suppose the NM has been too sucked into the borderliine nonsense to address that.
When I have a borderline pt with those types of behaviors, I make it known to other staff that any and all questions from that patient are to be directed to me by the patient. This eliminates staff splitting because no one else is involved in the process but the patient and me.
What do you so when someone breaks the rules there? Is there a more restrictive unit where she can be sent?
Any day that a borderline pt signs a request for disharge form is a huge victory in my book. They *want* to stay. In your situation, offering the patient the opportunity to initiate the process of signing herself out was perfectly appropriate, IMHO. I usually just give the standard line: "I'm sorry you feel your needs are not being met here. Since that is the case, I will get you a form to sign that tells the doctor you wish to be discharged. I don't want you to stay somewhere you aren't comfortable." No arguing, no drama, repeat as necessary. Naturally, they will either not sign it, or later tell the doc they have no desire to leave. But repeat until they realize that the situation is what it is, and they will follow the rules or they can leave.
Please update us on the situation!