If Astoria knew what Ron was currently thinking she would be telling him it wasn't a matter of them being easy or not, it was a matter that some people don't actually like their questions going unanswered.
"Fair enough," she said. It hadn't the answer she'd been expecting, but since she'd said the same thing moments earlier and was believed, then she ought to give Ron the same benefit - even if she did suspect there was possibly another reason he wasn't willing to mention.