"Thank you Jane for bringing this to my attention. I appreciate your input. and I will follow up" And follow up, however, you are under no obligation to then share with the CNA the details of the outcome. In other words, to explain that there was a mix up in communication is then putting the issue back on her to comment and evaluate. "I so appreciate your insight, and thank you, the patient is stable at this time".
That this CNA wants to run around and look for ways to make herself a "real live hero" is not your issue. Irritating, but not your issue. You went in and assessed the patient. The patient was stable. You did the correct thing in involving another nurse to also assess the patient.(that the CNA said you were making the wrong move is a moot point, ALWAYS get a second nurse's opinion when a third party brings something to your attention like this), The patient was stable. Document the same. Should the CNA question your nursing judgement again, and your head nurse looks at you like you have 3 heads, I would fall back on the fact that you can't be everywhere at once, and a good CNA is your eyes and ears when you can't be. So you should always follow up and err on the side of caution. But limit the details on your interventions and outcome so that the CNA can't comment on them. And if you are not crazy busy, I would say something to the effect of "what a wonderful teaching moment!! What is it that you would have done in this instance? I would love to talk to you about what you would do, it may help you in your clinicals!" (<---I am saying this WAY too sarcastically in my head......but you get what I mean). As an aside, that you involved the head nurse was a good thing, as in fact, if this CNA, who is a nursing student still, shows questionable clinical judgement and continues to comment on the nurses it will not go un-noticed. And in fact may be taken into consideration should she then seek a job on your unit when she becomes a nurse.