Oof, Marcia, this doesn't sound good! I can understand why you'd be concerned!
The lack of communication, combined with the observations from your neighbor, are certainly worrying. Without more information I'd hesitate to take action. It could be as innocent as a guest who doesn't have the app installed (not receiving notifications). Or it could be that she's filled your house with extra people and is ducking your calls. If I couldn't reach her via phone call, I'd either show up in person or send a reliable friend.
You could also ask Airbnb to cancel her, due to the unresponsiveness and report of extra people, but whether you could do so without stiff penalties is another question.
To eliminate further issues, and since you're not close to your listing, I'd seriously consider getting a few cameras to monitor your exterior doors. It's an enormous amount of reassurance to see - yep- that's the person who booked and -yep- that's the # of guests they reserved for. -Whoa- is that a (Dog, Stripper, Keg) coming through the door?!? (Plus you have video evidence)