Steve Huxham's Answer:
It may be unusual to answer a question with a question, but I am bound to ask, as I read further into your dilemma: just WHO is the problem here?
Is it with the employee and her apparent willingness to engage with (worthwhile) projects at the expense of time for her "basic" duties? Or is the root of the problem actually with the supervisor or the rest of the team? Or, dare I say it, even with you as a manager?
The most telling comment I read in your piece appears a few lines from the end, where you state that "she's an earnest employee (in contrast to some of the others).
What a statement that is! That is why I pose the question of who the problem is with.
Firstly then, I have to answer the question in the context of respect for good Talent Management strategy. Here you have a dedicated, and engaged employee who stands ahead of her peers by her dedication and goes beyond the call of duty to help and support others - something which by the way, you agree is at the heart of the company ethos.
Most sensible, forward-looking employers who want to nurture their talented people would be working closely with this individual to encourage them surely, rather than fretting over their time management?
Perhaps it is simply a case here that you have someone who is an undoubted asset to the company but whose innate and collaborative skills are not being used in the right job by you? Is she avoiding the "basic" duties because she feels they are beneath her skills and worth to you? What are her aspirations for the future - what themes in terms of where she wants to go with you having you been picking up in appraisal over the last 6 -24 months?
If you do not have that information at your fingertips right now, then I would suggest you need to get in with some one-to-one consultation right away and get some answers. No company on the planet can afford to see assets like this person become demotivated and potentially exit.
Moving on, I revert to my questions at the beginning. There the obvious follow up one for starters - if you have other members of the team who are not "earnest", and with due respect, shouldn't you and your supervisor earn your management salaries by sorting them out first rather than pick on this individual for a trivial "transgression"?
Prioritise please! If you don't and she and other "earnest" employees see you picking on the wrong targets first, you will lose their respect so fast you won't believe it.
Finally, your supervisor bothers me here. What is his/her role in all this? Why are you asking the question, when surely it is in the Job Description of the said person to be on top of such matters rather than come running to you with the problem?
Looking at what has happened another possibility here troubles me. One could read your description to imply that the employee, in her efforts to support others, is actually doing work that the supervisor should be doing? Is this employee aware of your supervisor's shortcomings and trying, through her dedication to the business, to "cover" for him/her in some way?
Whatever the reality, and aside from anything else you do, I can't see any alternative to having some serious conversations with your supervisor on this topic straight away. There appear to be issues running throughout the team and you need to get with the plan and show real leadership to sort them out from the top down.
Good luck!