It sounds like your puppo just needs more help learning to be comfortable around people, through continued positive exposure and training :)
My dog is a year old now (working Cocker), and he barks A LOT. He was poorly socialised, and he's very nervous of men and kids. He's unsure about new women, but warms up to them much more quickly. We adopted him five months ago, when he was 8 months old.
He barks whenever he hears noises outside the front door, outside the window, or on the other end of the phone if loudspeaker is on. He's also territorial about the car and will bark wildly at anyone who walks past, when he's inside.
All of the above, I consider to be problem barking. It means he's oversensitive to sounds, because he thinks every sound is a threat / worthy of alarm. We're trying to work on desensitising him to this. So far, no improvement - but I've been focusing more on other issues he has, so that's on me mostly.
He barks like crazy when our front door actually goes - but I appreciate this. That's normal for a dog. That's just "alert barking". Once I'm answering the door, he knows to go to his place and stay put, quietly (and he does this brilliantly).
On walks, he will bark and lunge occasionally, when seeing certain strangers (usually men). He does it when he feels threatened - for instance, if we're on a narrow trail, or if someone comes out of nowhere. This is gradually getting better through "look at that" training, but we have a way to go.
When someone enters the apartment, he goes absolutely postal. Similar to your doggo. What helps is either the person leaving the room (say, a contractor); or otherwise, having him on lead (for the person's safety), and letting him be close to us, so he has the ability to suss the person out.
We're planning to book a behaviourist to help us with his fear of strangers (which will help the barking). We've done lots of work with him in the 5ish months since we adopted him, but we want to make sure we're doing the right things. Sometimes it's difficult to know what's working and what isn't, as it can take a long time to start seeing progress.
Good luck with your doggo! It sounds like you really care for her, which is beautiful!