I started in my new role as manager 6 months ago and she just came back from ML.
My manager (who used to manage her) just told me she hasn't been happy for many, many years, but that she has stayed even though it's very apparent she isn't happy.
We're thinking of starting to involve HR as her quality of work is subpar (she's already been on a PIP before).
I'm new to this role so don't really know how to proceed. When it happened to me, my then manager told me she's help me "leave" (although my circumstances were slightly different).
So AIBU to think we need to build a case? Being unhappy is obviously not a reason for dismissal. Or somebody has to be brutally honest with her, but that might backfire.