How my friend accidentally discovered her passion for busting balls

My friend (F) and I were recently chatting and I brought up how she has a weird obsession with balls. This wasn't a creepy way for me to introduce my fetish into the conversation, she really did *always* talk about balls and doing unspeakable things to them (e.g. she once threatened to stab my other friend in the balls and has threatened my balls occasionally). But I could never tell if she was truly into ballbusting stuff or if she just said that stuff to be shocking.

Well, she told me her "origin story." Apparently, in high school she played volleyball and some of the practices were co-ed. One day, she was on the court in a scrimmage and she and one of her male teammates both dove toward a flying ball. They collided and she accidentally kneed him in the balls really hard. She said he had to sit out for the rest of practice and later told her it was the worst pain he had ever felt in his life. She felt bad, but she also said that it made her "feel really powerful."

Apparently since then, she's always loved the idea of hitting guys in the balls, though she's never done it since. Earlier that day in an unrelated conversation, she asked if I thought she came off as intimidating. After she told me that, I said she was intimidating, if not just plain scary. She laughed and said "well, just don't make me angry." I couldn't contain myself so I egged her on; she has bad knees so I replied that she probably would hurt her knee if she tried to kick me. She just smiled and said, with no hesitation, "If you made me angry, I would gladly dislocate my knee to make you feel the worst pain of your life."

She then told me she was just kidding, and we switched topics. But oh my god it was so hot.