This also works for male friends too. Make it a brag.

Tell folks that your homie right here got the best pump game and easily the tastiest penis.

Risky, but satisfying

What do I do when I reject a girl so she tells everyone I tried to molest her?

Personally I would go for something subtler, like: “Lets just say theres a reason hes bragging about it and im not.”

Oldie but goodie

No, because that acknowledges you thought he was good enough for you. Also, you’re lying, and no better than he is.