We are at the lake and our 16 year old grandson & friend are staying with us, Abbey loves all people and has been fine with them for 3 days before this. Last night seemingly out of the blue she took a dislike to the friend, he's a great kid whom I've known all his life and he's a dog lover to boot. His family has labs and he's very involved with them. The boys drove back to camp in the golf cart and the girls did their initial bark thing, then when they walked in Abbey did a low level growl thing and lifted her lip. It was definitely directed at the friend and she wouldn't even take a treat from him, she had been all over him getting petted 2 hours before that. We are stumped. He said he'd petted another dog while they were gone, but really, would, could that be it? Today not as bad but she was still very apprehensive. If my dogs ever react to someone like this I take note and believe they sense something I don't, but I know this kid, and even if I didn't he hasn't been alone with her. Any ideas on what could be happening, or how to respond to her fear/uneasiness?