Will, at this point, after looking at all of your previous posts, there is a common theme. You are highly anxious and often irrationally so. You also have quite the busy sex life and would doubt that a woman you know puts herself at more risk than you do yourself with CSW's that you frequent. So, giving perspective here as you write about this woman and this situation that is not that much different than all of the other situations you've written about over the years here. You used protection. Your risk is low with a condom. However, if it was pushed up, in that small area (and it is small along with a small risk), you would have the exposure of any std's that transmit skin to skin. You likely know what they are since you've asked so many similar questions. Herpes, HPV and Syphilis. In the absence of symptoms, I would not worry. And that it was for a minute? Less of a worry. But since you worry a lot, what about talking to your doctor about anxiety? It is treatable.
I would like to add that the protected vaginal sex was brief, like a minute or so.