My Suzi is all of a sudden becomming more vocal

Today, was the very first time she scared a person away who was coming to our front door!!!! I saw the individual though the window and Suzi went crazy. SHe has the loudest, most alarming bark ! I older kid was right at our front door, and turned around without even knocking.... I wonder if he would have knocked if he knew our pup is a full 7lbs , LOL .
How many others have a loud , scary , little barker? The funny thing about Suzi is that she loves people.