scared pup

Not sure what's up, but I've noticed Sophie's been acting a little strange. Mostly today, but for a few days now. Two days ago a neighbor came into the yard, all the while talking to Sophie. I wasn't there, but my parents were and recaped this story to me. Sophie started shaking and dropped to the ground and softly growled. She was acting scared and unsure. Ok..., except she's never displayed this reaction with this person before or anyone really. Then today, I noticed that when I told her to go in her kennel or when I took her out to do her business, she started to shake uncontrolably. Not sure what has changed to make her so timid and anxious. I'll be keeping an eye on her and rewarding positive behaviors.