Is this gal single or married? Because if she is married or in a serious relationship then I can practically guarantee she didn't tell her husband (or SO) about the car ride, either.
If she is single (which I suspect is more likely), then her wedge-driving behavior seems to be not necessarily that she wants your husband but more that she wants male attention. If she's unhappy with her job or her living situation or the choice of men in her area, then she's possibly craving attention.
Also - seriously - I grew up someplace other than where I currently live but I don't call going back to my folks' house "going home". If she still thinks of going back to your city as being "home" then she may not be fully committed to where she is now.
But back to them. There's not necessarily anything going on. But she is, like Punkey said, trying to drive a wedge. My husband has female friends and they don't do this kind of wedge-driving. Hell, I despised my best friend's first husband but I never tried to break up their marriage or gaslight him.
Something else is going on here.
Good on you for going to counseling. Get some tools for dealing with this.