Kiss up Kick Down direct causing havoc

Hello all- I have a direct report who is causing havoc in my team. She is great to me, nice, professional, and does a reasonably good job. 
Apparently to my directs and her teammates it's another story. Every time I am out of of the office I get a report this direct had an "episode" and yelled at someone, tore someoine down or has acted unprofessionally. This one is difficult to tackle because I have not been witness to the actual behavior. 
Based on the feedback I am getting not only from my team, but the rest of my building I have strong reason to believe them. I have also had a supplier complain about working with her. 
How do I start this conversation with this direct about her behavior while I am not in the office nor have witnessed it?