Pugs are small (under 20 lbs) and fantastic with children. They are sturdy too which is a bonus when a small dog is around kids. But, they won't really bark at people. Instead, they will do whatever they can to visit and greet a new person...tailing wagging and body quivering with "pet me" anticipation. Pugs love people. They are charming and outgoing. A well bred pug is rarely, if ever, suspicious.
If she just wants a dog that barks at the door bell then a pug might do that, lol!