He underestimates how desperate other men are.
Her poor attitude certainly doesn’t turn away those hitting up her phone, so why would some stupid lie make any difference?
Oh, whatever will he-start a rumor.
See, attractiveness comes with reputation. But, if you destroy the reputation, the attractiveness fades into grotesqueness.
She's going to say something snarky and tell him it won't work, but it will. And when it does, he'll be there.