@mchalel,
I think there's her story, and his story, and the truth is somewhere in the middle. If this woman is not claiming they are seeing each other, NOW, block her, and don't respond. She does sound a tad histrionic, and like someone he may have led on, who just couldn't handle the rejection, when it ended. If you're happy, and don't see any other signs of cheating, then live your happy life. If hubby is online at all hours, or insisting on a phone pass code, or ANY secretive stuff, then, there might be grounds to be suspicious. My husband and I could pick up our pones and look through them at ANY time. That's what keeps us out of the crazy and suspicious zone. In the age of online married cheater's sights and crazy ex gf's texting and harassing, you need to be aware, but not hyper vigilant.