It sounds to me like she's unsure (afraid) because she's now in a new place and your parents aren't there, either. So I don't think it's territorial aggression, but I've been wrong many times before. If it were me, I'd put her in her crate when someone comes to the door until she's more settled into the new place.
Wrath of Grim z Dragon
"Mr. Grim"- Threaten my handler. I dare you.