Tell her that! Paraphrase that statement and it would be perfect!
Tell her that in your opinion, she is an excellent nurse, is well-liked by the patients and staff, and a great resource. Tell her that even this is a learning opportunity, and atleast the "first med error" transgression can be crossed off her 'hasn't happenned yet' list.
After stating that, I would then ask her why she thinks it happenned. Take her aside and be like, what was occurring at the time when she made the error. Brainstorm with her tactics that she can use to hep prevent this from occurring in the future.
I hung the wrong primary bag on one of my patients. Thankfully, no harm had come to the patient but I was rushing and had grabbed the wrong bag. One of the more experienced nurses who cought the error told me that I should try to scan the primary bags too- that would have prevented the error. She also told me that she understood that it wasn't always possible to scan the bags so what she started doing was she just slowed down and when she was labeling the bags with her name she also started putting a check in one of the corners of the sticker that meant, to her, that hse slowed down and checked the bag against the orders.
It was a great tip and is one that I have implemented.
So much about nursing boils down to HABIT and routine. Small alterations to a person's routine/habits can really have a large impact on patient safety.
My point is to focus on helping her alter her behavior to help prevent future mistakes. Also, brainstorm with her if she thinks any system errors also played a role in the error....could the two cards have been placed further apart so that they aren't so easily confused? If so, encourage her to discuss it with the DON.
My point is help her change her thought process from "oh no i'm an awful nurse and an awful person and I just suck" to "this is the problem, this is how I contributed to the problem, this is how the system contributed to the problem, and lets think about how we can fix the problem."