How would you define a stutterer who doesn't stutter around people they know but who stutters around strangers?

How would you define a stutterer who doesn't stutter around people they know but who stutters around strangers? My aunt stutters. The weird thing about her situation is she doesn't stutter around the family. What I mean is she will barely stutter on any words when at home with us and just chatting. If she meets a new person or is out and about by herself, she will stutter. It's honestly the most peculiar thing and I was curious if there's a term or name for this? Would seeking help with this type of stutter be different than seeking help with other types? My gut instinct is it may be related to an anxiety issue that is presenting itself in a stutter.