When she heard about Harry’s confrontation with Tom Riddle’s spirit in the Chamber of Secrets, she knew exactly what had gone on. Harry had destroyed a Horcrux, damn the silly boy! Those weren’t easy to make. Poor Tom. Paimon wasn’t happy to hear about his old favourite losing one of his precious ties to immortality, but assured her that he’d checked, and Tom had backups. She wrote to Lord Voldemort anyway – and had an imp (house-elf) personally deliver the letter to get past his rather comprehensive mail wards – to warn him that he’d lost a Horcrux. He didn’t say "thank you" in quite so many words, but she did earn a promise of his favour. Along with his return letter he also sent a gift of an extremely rare tome of Dark spells which was enchanted to look like a dull book on the history of toads, to any curious spying eyes.