The stories in the first chapters of Luke undoubtedly had to come from Mary. Luke could have interviewed Mary or possibly John (who was made Mary’s son at the cross) or other family member.
On this note, I have a theory that a common source for the synoptic gospels is one or more of the scribes who were often present when Jesus spoke.
Yeah, no way the Holy Spirit could have known those stories, had to be a Marian interview.