I understand your frustration. You didn't reveal the position/role of the person who "counseled" you but I can suggest some follow-up activities to turn that lemon into lemon meringue pie.
IF that person has direct knowledge of your job performance (e.g., works the same shift, has observed you at work) you need to alter her/his perception. Make an appointment to discuss specific actions that you can undertake to 'improve' & meet her/his expectations. Keep probing until you get a clear idea of what success looks like for this person. Be prepared for some weirdness. You'll have to ask probing questions, because chances are that anyone who is this bad at providing feedback (vague & non-constructive) will try to be vague with you also. For instance if he/she says "you just don't hustle when things get busy"... you could ask "what type of activity do you want me to be doing?"
If this person was making judgments based upon second-hand information provided by others, you'll need to take a different approach. Remain objective and professional - make it clear that your intention is to improve your job performance. Focus on uncovering the specific criteria that were used to evaluate your behavior. (respectfully) push past the ambiguities until you get clear descriptors of what is expected. You may have to suggest the criteria yourself. For instance, you could ask "When there is a lull in patient activity, what tasks should I be doing?" or "Before updating care plans, checking orders, or other non-patient care work, do you want me to check with everyone else to see how I can help them?"
Very important - do NOT say anything negative about your co-workers, even though they are probably the ones who actually precipitated this unpleasantness. Instead, make sure that your 'counselor' knows how much you respect and admire them (erk, I know - but keep from looking nauseous). Since this person obviously is into gossip and inuendo - this message will also be relayed back to that peanut gallery. If nothing else, it will confuse the heck out of them. LOL!
Hang in there. Chances are, the meanies will have a new victim soon and let you alone.