"If that's true then you can't go until I figure this out." He can keep track of how persistent her amnesia is. If he leaves, she'll have to resort to leaving Memento-like clues on her body or gouged into her walls. That she hasn't found any before now and can't see any from here, is how she can tell she's having this breakthrough for the first time. So she might not forget again but Jess won't bet on it.

"Could someone do this to me? Was that on the machine?" If it was, she could do it to herself but Jess doesn't understand why she would. The things she wants to forget are too scattered around her past for her pain to be excised with a blunt instrument.