I think a key issue here is how the employee came to you in the first place. Is it as a result of a self or management referral and are you expected to feed back to anyone?
 
If its a self referral then all the comments below useful, in addition I would say that the company must have a grievance/mediation policy that she should explore for management channels through which to take her concerns. fact is that she needs to voice her concerns to someone other than OH if a solution needs to be forthcoming. Perceived advocacy is something (in my view, and I`m not saying that this is happening here) that should be avoided in such situations to maintain the integrity and reputation of the OH dept
 
If its as a result of a management referral and feedback from OH required then its the usual recommendation for stress RA, and maybe mention that "mediation or other management processes may be more useful than clinical intervention at this present time"  to take the case forward.
 
As we all know -  only having one side of a story can be misleading, it may well be that the manager in question has valid issues with the employees performance and we all need to be very clear that we are not "taking sides" as could lead to all sorts of difficulties in the future and may even backfire