I Watched My Best Friend Emotionally Exploit a Boy at Dinner

I witnessed something a couple of months ago that left a terrible taste in my mouth, and I haven’t been able to stop thinking about it since. My best friend is gorgeous. She knows it, commands attention wherever she goes, and is fully aware that guys fall over themselves just for a minute of her time. One evening at work, she called and insisted I join her for dinner at an upscale spot. When I asked what was going on, she casually mentioned that a guy—let’s call him X—was taking her out. X was head-over-heels in love with her. The kind of boy who would move mountains just to see her smile. She knew this, of course, and regularly let him take her to expensive lunches and dinners just to have the bills covered. When I arrived, the dynamic was already painful to watch. He was trying so hard to impress her, laughing at every word she said, completely oblivious. We finished eating, and the check arrived at the table. That’s when my friend leaned into my ear and whispered something with a smirk: "Watch this. I’m going to pull cash out of my purse, hand it to him, and tell him to pay at the counter. He'll take it, walk up there, pay entirely with his own card, pocket his own loss, and return my cash back to me." I honestly thought she was joking. Then it happened step-for-step. She handed him the money with a sweet, innocent smile. He gladly took it, walked to the register, paid the entire bill out of his own pocket, walked back, and handed her cash straight back to her like a proud gentleman. I sat there frozen. He genuinely believed he had won her respect, while she had just orchestrated his humiliation like a parlor trick right in front of an audience. When I confronted her afterward and asked how she could predict that so casually, she just laughed and said, "Experience." I felt sick to my stomach for him. I wanted so badly to pull him aside and tell him he was just an ego boost and a free meal ticket, but I stayed quiet. Why do so many good, genuine guys let their self-respect get destroyed by pretty faces who don't care if they sink or swim? Where is the line between being a supportive best friend and calling out someone's outright cruelty?