Chickens are not mammals and don't get colds per se...Chickens get sneezy from time to time, but as long as there is no drainage or wheezing then you are usually alright if sneezing is the issue......
I didn't watch the whole video, but how old is the chicken? How long has she been laying? Have you gotten any new chickens recently? Is she coughing, wheezing, any drainage from anywhere on her face? Mouth, Nose, Eyes?
Has she taken any poops? Do they look normal?
If you aren't already giving her some sort of vitamins in her water I would start...if she won't drink it give it to her with a syringe with no needle for like baby medicine...You can also try some of the meat baby foods if she still won't eat...
Check her crop, and smell her breath...and then get back to us, and we might stand a better chance of how to help, because a chicken with a drooped tail refusing to eat, is the first sign of any and every chicken illness...so it could be anything right now.
Here is a list of Zoonotic diseases that can be passed from person to bird or bird to person...
Avian Influenza
The H5N1 Avian Influenza virus is a well-known and deadly zoonotic disease. It is transmitted through coming into contact with the fecal matter of infected birds. While H5N1 isn't seen as a particularly common threat to captive pet birds, it is possible for any bird to become infected and transmit the virus to other birds and people.
Avian Tuberculosis
Tuberculosis is another familiar name in the world of diseases. Avian Tuberculosis is caused by inhaling microscopic airborne organisms that are shed in infected birds' feces. This disease can be hard to treat in both birds and humans, and can be fatal for some.
Campylobacteriosis
Campylobacteriosis is a bacterial infection that causes gastrointestinal problems. It is usually transmitted through fecal contamination of food and water. While diarrhea, weight loss, and lethargy are common, Campylobacteriosis can also be present in birds that show no symptoms of illness.
Chlamydiosis
Also known as Psittacosis and Parrot Fever, Chlamydiosis normally produces symptoms such as eye infections, diarrhea, and respiratory problems. Highly contagious, Chlamydiosis requires swift and vigorous antibiotic treatment as well as placing birds under quarantine to prevent the spread of infection.
Cryptosporidiosis
Cryptosporidiosis is caused by a microscopic parasite called Cryptosporidium that takes up residence in the intestines of its hosts. The parasite is transmitted through the consumption of food and water that has been contaminated by the feces of an infected animal.
Giardia
Giardia is another intestinal parasite that is transmitted through the ingestion of contaminated food. Symptoms of Giardia infection include severe diarrhea, weight loss, and dehydration.
New Castles Disease
Although New Castles Disease is more commonly seen in wild birds, it can affect parrots and other species that are commonly kept as pets. New Castles Disease is a virus that causes neurological dysfunction, seizures, and respiratory problems. It is transmitted through oral and fecal fluids