Emma raised a good point. Was Ashley trustworthy enough to handle the truth of who and what he was? Even if he wasn't a vampire or a werewolf, or anything else that carried with it an innate negative connotation, the secrets he had were secrets that he wanted to keep. Ashley herself was a witch, but she didn't know that. How would she react to the idea that not only did she have as access to magic that she'd never known about, but also that he had been the one who had — in effect — kept that power from her? Would his reasons matter at all?
Xander nodded thoughtfully. Yes, let her think it was rhetorical. She was correct, at least, in that he would have to figure out the timing on his own. Ashley's grandparents couldn't keep the truth from her forever, and — if he were honest — he'd prefer they be the ones to explain their decision to have her magic bound, before even more time passed and he found the responsibility landing squarely in his own lap.
After a silence, Xander lifted his gaze to the vampire sitting across from him and he smiled. No need to cause Emma any concern. Things would right themselves — eventually. They always did. That was the beauty of time. It brought change, whether you wanted it or not. After over a thousand years, he'd learned that much. He tried not to let his eyes betray his more serious thoughts as he teased her. "You know, I'm expecting a very nice souvenir from London when you return. One that isn't reflected on your expense report for reimbursement."