Dog has gotten mean

So I have a 4 year old 40 pound mixed lab. She's always been shy to strangers, but she usually barks and hides. Today, for the second time, she charged and tried to attack someone who works at our apartment complex who came inside. She didn't get him, she went for his shoes. But I'm so scared they could kick us out over a mean dog. Also, I'm 35 weeks pregnant. How do I know she won't be this way around the baby? I have a 9 year old step son who literally jumps on her and she's never as much as growled. Could this just be because she's protective of me while pregnant? I'm bawling crying because I don't know what to do!!