My border Collie nipped at a woman today. My dog was sitting between us as we chatted. As the woman went to go, she suddenly bent down to pet the dog (she has petted her before - used to regularly meet her on walks) and my border collie reacted badly. The dog didn't break skin but nipped her on the hand to let her know she wasn't to be touched. A man on my road used to regularly pet her too - but the day I got her out of a boarding kennel (she was there three days), he went to pet her, and my dog would not let him near her. Bared her teeth and even at me when I tried to control her. In both instances with both people, after baring her teeth, she goes behind my legs and cowers when they try to talk to her and get close to her.
What is going on? She lets me and family pet her all we want - big on cuddles and everything. A very affectionate dog.
Do I need to bring her to a professional?