If she impugned you via email, and copied that email to a large list, you should have refuted her via email and copied your reply to the same list. Something along the lines of “Jan, you don’t know what the hell you’re talking about and here’s why—.”
I had a situation at a job some years ago where a co-worker was trying to find a way to get me fired. One time I had signed out some tools to use off site, without bothering to check, he told the VP of engineering that I was steeling the stuff! This didn’t earn him any points, but he didn’t give up there. A few weeks later there was some unused equipment in the lab, he kept telling me that I should take it. After hearing this several times I got an idea, disassemble it and put in storage behind some other stuff. Well within days the VP was there looking for it, sure enough the little weasel had said the stuff was missing, and he knew that I had taken it, even said he saw me do it! He was in meetings most of the rest of the day. He managed to keep his job, but just barely.
Yes, reply to the same list, but say “Jan, I don’t understand your email. We discussed this matter earlier and you admitted that the error was yours.” This should drive her absolutely psycho.
Javaman, please respond to this thread and let us know what the situation is. You should receive an apology from Jan, at the very least. You should also contact your supervisor at this time, in my opinion.