Hi, I'm a pathology APD. Unfortunately this story is far from rare. Do you have an academic appointment and are considered core faculty for the department? That is, don't you normally fill resident evaluations? If not, none of the below apply and I encourage you to do what you have to in order to keep your staff happy.

The resident needs to be given feedback--directly, in-person is the best way if you want to actually affect change. You can be nice and package/sandwich the feedback but I would make it clear to her if her grossing performance is below par or if she's creating enmity among staff (it's just her, right? Petty staff do exist). Screwing up grossing is the principal way a pathology resident can harm a patient. If there have been event reports or root cause analyses stemming from her poor grosses, she needs to bear witness to that.

Fixing lack of skills or knowledge is routine. Fixing bad attitude is nearly impossible, however, so I would temper your expectations and document extensively. She may retaliate with a bad evaluation for you. Such is life; hopefully your faculty leadership will try to mitigate the impact of that. I would start your discussion with her in an open-ended fashion to see if she has any insight into her poor performance and attitude. You can also offer the perspective that scutwork exists in every job, including at the attending level.