Sentence:  And I'm talking about seconds that mean so much! that will let us rewrite our histories—<WSD>unwrite</WSD> the letters that Allie wrote near that time; <WSD>unwrite</WSD> her time on the beach with Johnny; make us both virgins exactly as I'd seen it then; <WSD>unwrite</WSD> my times with Barbara, my phone conversations, letters, years of druggy dreams of her, and my revenge story and all of Allie's times with Lemaster. 
Meaning of the word marked with <WSD> tags:  To nullify.