I can't believe how similar everyone's stories are!!!
My husband's DD started exactly like that, with small incidences of "rewriting history." I even called him out on it, by saying things like "hey, that didn't happen" or "I/you/he never said that." It was no use. He was repeating and repeating the same incidents from the past for weeks, like an obsessed broken record. Over time he kept adding more and more detail, and I kept pointing out that no one could possibly remember word-for-word entire conversations from almost ten years ago. I would point out "You just added that from yesterday when you last told me this story" and he would say no he didn't. No matter how many times I pointed it out, it was no use. He didn't see it and denied it. This was in the early stages of his mind going, before I even knew anything was wrong. I just thought he was obsessing so much that he was creating conversations or something. Eventually I realized they were becoming delusions and that he was truly mentally ill, at which point I completely had a breakdown and started having panic attacks myself. It was awful.
I think Bri hit the nail on the head above. The delusions were appearing and then rather than face the reality that something is wrong and they may be mentally ill, they next start by rearranging facts in their mind. These then become the false memories that plague them and everyone around them. It's horrible to be the center of these jealous fake memories. We've even had contact with other people who were around back then, who have no idea what he's talking about and he just says they are all lying. I remain the evil whore who did all these disgusting things and now he hates me for it....my children have heard it all, our friends have heard it all....false memories and rewriting history can kiss my butt. Sorry, but I'm just angry still.