My 2 dogs were in a kennel 3 weeks ago while we were away. Dog #3 was at Grandmom's, puppy#4 was back at the breeders. All but puppy have the KC vaccination.
Found out when I got home the kennel had a boxer who was coughing. They immediately isolated him, but it was too late.
My 2 dogs brought KC home with them, but didn't have any signs til 2 days later. It's spread thru the air. You shouldn't be able to bring it home to your dogs unless the other dog comes with you (unless maybe she had dirty hands, or somebody sneezed or coughed on her before she left home). Could be your friends dog caught it from a stray dog passing by, etc.
Now all 4 of my dogs are sick. (1 coughing up mucus, 1 just sneezed a few times, 1 coughing but no mucus, 1 sneezing her head off).
Kennel Cough is like the human cold. You should get the vaccine, but the disease mutates itself constantly, so still a risk your dog can catch it. But supposedly, if they catch it, it's not as severe if they've had the vaccine.
Vet put my 2 dogs on an antibiotic, 1 on cough meds. The puppy is on clavamox and cough meds. This can linger for weeks. The last dog isn't getting anything until I know if she's going to do more than sneeze.
Make sure she keeps her dog away from any other dogs or she'll spread it (no contact needed).
If one of the lady's dogs had KC, they all do now (could just be different severity in each like mine)
That frickin vacation has cost me over $700 just in kennel and vet bills so far the last 2 weeks. Next time we're getting a house sitter.