Pansy (Draco's Girlfriend) attempts to blackmail Harry with the information of what he did as a young wizard, which was pleasuring a older witch as a second or third year, fail miserably, and Harry could simply take pity on her and give her a way to get the thing she wanted (extra money) by offering her generous pay so long as she comes to him whenever he bids her; and before long she's hooked on his cock.
Deco never finds out about this until after the last day at Hogwarts where Pansy breaks up with him while telling him 'I found a much better boyfriend.' Could be in private or in public.
