Guy's Behavior

Should I tell this girl that this guy is leading her on?

My engaged supervisor has been leading on this gorgeous supermodel looking girl in my office. She is very sweet and quiet. My supervisor pretty much flirted with her until her wore her down and when she finally began to catch feelings and show interest, he cruelly rejected her and keeps humiliating her. Although, he rejected her he keeps flirting with her, then pushing her away. He deliberately flirts with women in front of her. One day, she snapped on him for trying to make her jealous and her made her apologize. She wrote him an apology note, and I heard him in the break room bragging about how he has her wrapped around his finger and how he can do anything to her she’ll still be into him and how this has been going on for over a year. He also laughed at how she’s turning down other guys for him.

I feel terrible and wanted to punch this guy in the face, not just because he gets upset when he sees me and her interacting but because he’s such a dick. Should I tell her what this guy is doing or should I stay out of it?
Should I tell this girl that this guy is leading her on?
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