You have to come to terms with the fact that they are both going to lie and somewhere in between lies the truth. How important are the lies in the grand scheme of things?
In my case, he says they used condoms, she says they didn't. He says she wanted to have anal sex, she says she didn't. He says they continued contact via fake email for several months after Dday. She says they didn't.
So, what it boiled down to for me was how important the lies are in the grand scheme of things. I've already thought the worst. I figured they didn't use condoms. He swears they did. I came to terms with the likelihood that they didn't. I know they had sex in pretty much every way already. Does it really matter if it was or wasn't anal? No, not really. I know they were still in contact because he was still hiding his computer for some time after Dday and why would he lie about that? It would be nice if he never contacted her again but she's doing damage control with her own husband so I know my husband's version is probably true.
Deep down, you know your husband. You know when his actions match his words. Do you feel that he is really doing everything possible to be truthful from here on out? If so, then are little details enough to warrant further damage to your marriage. And, if not, are little details enough to save it. That's what it boiled down to for me.
Of course, the OW is going to remember things differently. She is going to read into every little thing and put her own spin on it. And remember that she likely has an agenda. If you can independently verify, great. But if not, weigh out the importance of the information in your mind and then compare to the actions and words from your husband. You'll have your answer about how to move through it from the combination of those things.
And tell the OW not to show up at your house again or you're calling the cops. You don't need that when you're trying to reconcile no matter what information she thinks she has.