Hermione told Draco that she wasn’t in the least surprised when Ron started dating Hannah Abbott. Apparently she used to witness them flirting at The Leaky Cauldron all the time, and had suspicions for a long time that something might be going on – though he never cheated, or at least not that she knew of. Draco would have remembered more details if he gave a shite about her ex. He doesn’t fault Hermione for wanting to stay on good terms with him, though.