Obviously, colleagues find this unsettling. I can't figure out whether this is just attention-seeking (we know some of it is made up), or a sign of mental illness. If this were a straightforward work-performance problem I would have no hesitation in tackling it, but because she strikes me as mentally unstable I am worried about doing something that actually makes matters worse and prompts her to do something crazy. Your advice would be much appreciated.
A: You're right to approach this problem with the greatest possible sensitivity. About the only advice I can give you with absolute confidence is this: whatever you do - including doing nothing - do it with the knowledge and support of at least one other person. By the sound of it, any intervention on your part carries risk; but so, of course, would a decision to sit back and wait.
I don't know if you have a senior manager or an HR director with whom you can share your concerns, but share them you must. You need to talk through all the possible approaches, do your best to imagine all conceivable consequences, and then formally agree on what action to take.
As you clearly recognise, you have two responsibilities that don't necessarily correspond. You have a talented if fragile individual, who may or may not be mentally unstable. And you have the rest of your team to consider, whose work she unsettles. Your company, however sympathetic, would presumably expect you to solve the problem of the disruptive one as speedily as possible - and that, of course, is the tricky bit.
You mention almost in passing that she makes things up. If you know that for certain, I think it adds some urgency to the matter. Unlike erratic behaviour, lying is not open to different and subjective interpretations; you need to ask her about it. And again, I believe there must be someone with you. This kind of situation could easily develop into a her-word-against-yours confrontation - and that could devastate you both.
Be gentle, unthreatening and sympathetic. From her response to your probing, you'll learn a great deal: not least, I suspect, whether her behaviour is just an extreme form of mischief-making or derives from some mental disorder. If the former, there's a chance that a friendly chat could make all the difference. If the latter, don't be tempted to play the psychiatrist: there's too much at stake for all concerned.
Through her friends or her family - or through your HR department - make sure she receives professional advice. Meantime, while telling them as little as you need, reassure the rest of your team that something is being done.
Jeremy Bullmore is a former creative director and chairman of J Walter Thompson London. His book, Another Bad Day at the Office, is published by Penguin at £6.99. Address your problem to Jeremy Bullmore at: firstname.lastname@example.org. Regrettably, no correspondence can be entered into.