Sirius couldn't help but be a bit surprised by the answer. There were plenty of things that he thought that he could have guessed that James was going to be upset about -- but Lily remembering her time here wasn't one of them.
"Why?" Sirius asked, his brow furrowed as he gestured with one hand. "Isn't that a good thing?" He'd never actually asked how Lily had reacted when she first had found that James and Remus were here -- if she had believed them more readily than he had. He suspected she might have. Or, at the very least, he suspected that Lily hadn't tried to punch James in the face and then try to use an Unforgivable on him.
But, however Lily had reacted, it couldn't have been pretty. It had to have been better for her to come back already knowing, right? She had known that she loved and trusted James.