Toddler won’t talk to adults

Is anyone else having this issue with their toddler? My LO does not stop talking at home. Her speech is amazing and every day it gets better, but she won’t talk to adults unless it’s someone she is comfortable with! She’s been at nursery for more than a year now and loves going, the staff say she is so chatty to other kids but as soon as a practitioner asks her something, she goes quiet! She’s like this with some family members too, particularly men. I want to get her out of it as we want to start potty training soon and my fear is she won’t be able to tell anyone at nursery when she needs the toilet. Anyone experienced this and got any tips?