"Oh, Zoe, I wish you'd believe me." The stone flashed.
Zoe became gullible and believed EVERYTHING that Jen told her. Jen doesn't have to convince her of anything now.
"I AM your sister. And everyone's memories including your own HAVE been changed. I know it's probably hard to believe, but ..."
"It's not hard to believe. It sounds possible to me."
"Really? You're not questioning anything?"
"Why would I? If you say it, it's the truth. I believe you."
'That was easier than I thought it would be,' Jen thought to herself. She hadn't realised that she had made a wish to change Zoe's mind.