ok, i see several problems with this.
First of all, CNA's in my state are NOT allowed to dispense medication, period. I have heard of medication aides, but there are none in my state. Maybe this LPN thinks that your students are SPNs?
Second, ALL(well, most) of us have prepared meds in advance, especially when working LTC. However, She should not leave these pills on top of the med cart. What if someone happens to notice a juicy narc sitting in one of those cups? I would HATE to have to count with him/her. If she is going to prepare her meds in advance, then at least leave the cups in the med room.
Third, yes, you DO have a voice. HAve you told your students to REFUSE to dispense medication for her? Thats too risky, not only for the patient, but for your license. YOUR there w/ student NA, YOU caught wind of them dispensing meds, and it's YOUR @$$ if someone says something or is given the wrong meds.
I would def. say something to the LPN in question, and if problem wasn't resolved, I would speak to DON. Just because your using their facility doesn't mean your license has to be jeopardized like this.
Hope all works out, and I didn't sound too harsh.
P.S. I've only been an LPN for a short amount of time, and I was a CNA before then. Huge difference. Let your students know that what there doing is outside the scope of practice for CNAs. Would be a great time to discuss the nurse practice act!