Zoni does her alert bark every now and then when a stranger or strange dogs approaches, but I think it is primarily when she can't see the person well (she's looking into the sun or it's really dark). She does it a lot less now that she is older. You could be proactive and condition her to like it when strangers approach.

Another approach if she is food modivated is to have a bowl of treats by the door or give the people treats. At first they should just throw the treats down in front of the dog. She would learn to associate strangers coming into the house with good things and I'd bet her behavior would change over a little time. I did something similar for my dog for table training. Good luck!