How old is the dog? (ish?)
If she is truly guarding the home then I'd say your advice is good. If she's simply being fear aggressive then the best course of action is to instruct all visitors to completely ignore her. No talking, no attempting to pet, no eye contact, no offering a hand to sniff, no giving treats. Literally act as if there is no dog. That will ensure the dog does not feel threatened and can then feel safe enough to investigate the guest and get comfortable with them. As guests enter the owner should have the dog on leash and feed the dog treats to try and keep her focused and calm (so they don't have to deal with the barking) during that stressful time. Or put the dog in another room while guests are coming in. Once everyone is settled and the dog is not on the verge of reacting anymore the dog can be allowed to investigate (assuming she's not a bite risk) the guests. The guests must remember to ignore her even if she seems like she likes them. The owners should not let her investigate for too long at a time, they should periodically call her back for treats. If she is not safe to allow near the guests (she's a bite risk, your guests don't like dogs, or they won't follow instructions to ignore her) she should be leashed and given a food stuffed toy to keep her busy and prevent her from getting frustrated about not being able to investigate the guests. Or she can go in a separate room while they are visiting.
Fear aggressive puppies are a bummer, believe me. I just hope they don't make the same mistakes I did. They should never, ever try and force her to interact with anybody, no matter how gentle and encouraging you are trying to be. Even if you aren't really forcing but just trying to encourage by having the guest kneel down and talk gently. It just makes them more paranoid that all the people are out to get them.
