Part of Hannah really wanted to duck her head down and try to keep things going as smoothly as possible, but she knew she couldn't just sit by after Neville broke the news. Regardless, she and Neville were friends before anything else. Even if something came up between Neville's family to cause problems in their relationship, Hannah still would've been Neville's friend. As his friend - and as someone who loved and cared deeply - she couldn't take his Gran's silence on the matter.
After giving Lucy a small spoonful of the cut spaghetti and watching Lucy happily eat it, she turned back to add to the conversation. "I told him that whatever he decided, I would stand behind what made him happy. He did a wonderful thing and was brave to be an auror, but the task is still in good hands even now that he has resigned. Harry and Ron are doing a wonderful job working on rounding up the last of the Death Eaters, even with the setback of the escape." She kept her tone calm - far more calm than she felt, really. She didn't want to be condescending. She just wanted to make it clear that she wanted whatever was best for Neville and would make him happy, as any friend - or love - would.