I'm no ED RN, but that to me qualifies as a change in status, and I think the exam should go forward. She's not coherent, she's answering inappropriately, she's gone from calm to combative, her gaze has changed - I agree with the doc. If she is bleeding into her brain, they won't know without a CT. I would, just for my own CYA, find out if she has any family with her in the ED and make sure they're notified immediately. To me, this is shoot-now-ask-questions-later, and the doc is probably thinking if she's bleeding and I didn't find it, it's my behind. Chart the crap out of it. To me the benefit outweighs risk here.
My guess is the answer is you should refuse the exam, though, because this is nursing school
and they're not going to think 'real world' all the time - but the patient is clearly not rational and not oriented.