Trust your feelings. I don't think your psych nurse should ever offer to give meds to anyone she has not assessed, especially through a patient...but I am guessing she was talking about meds the 'friend' had RX for...
(sorry, a nurse myself...I have strong feelings about such things...no offense meant---)
Feel guilty, then let it go. You are not guilty. You made the right decision. And, if you would feel better, it would be OK to tell the friend you are not feeling comfortable with her behaviors. She might be angry....then again, she might be able to 'own up', or at least respect your boundaries.((((((((((hug))))))))))))