Hello. Thank you for asking your question on just answer. My name isXXXXX will try to help.
1. Could be allergy?
Most likely she has picked up an upper respiratory tract infection which is like a "kitty cold." It is contagious to other cats but not to people. To help her feel better, you can give her an antihistamine called "chlorpheniramine." It comes in 4mg tablets. Give her 1/4 of a tablet every 12 hours to help with sneezing and nasal symptoms. You can also use nasal saline drops to help with nasal congestion. Put one drop into each nostril twice a day. You can purchase both at any drug store. She will not eat well if she has nasal congestion and can not smell her food. It helps to warm the food in the microwave to make it more fragrant. When you take a shower, take her into the bathroom to steam out her nasal passages. She should feel better in 7-10 days.
2.Should I take her to a Veterinary?
You should take her to a vet if :
-she stops eating
-her nasal drainage turns yellow
-her eye drainage turns yellow
-she has difficulty breathing
-she has difficulty opening her eyes
3.She is 1 year old never been to a Veterinary only when she was altered.How often should I take her to a Vet.?
When she was a kitten, she should have had three sets of vaccines against respiratory viruses as well as a rabies vaccine. The respiratory vaccines were to be given three weeks apart. If that did not happen, she needs to go to the vet, and get one respiratory vaccine combo which will need to be boostered again in three weeks. She will need a rabies vaccine too. Then after that, she just needs to go to the vet once a year. Hopefully this will prevent further respiratory tract infections.