Hello, thanks for the new question although I am very sorry to hear about your aunt's kitty.
The nose anatomy in a cat is amazing, it is built to filter out micro-organisms and foreign bodies and has very fine, intricate bone anatomy and sinuses to do so. If this system is damaged unfortunately it can become a hiding place for bacteria and fungal infections to hide however.
Because this has been a lifelong problem for her we may have worsening of a primary problem or a new condition developing because her nasal architecture has never been normal. Has she been tested for immunosuppressive viruses (feline leukemia or feline immunodeficiency virus) recently? If not that should be done.
I am not surprised that she isn't eating as a big stimulus for a cat to eat is smell. They won't eat what they cannot smell, and if food is tasteless to them they often won't eat. I recommend continuing the appetite stimulant (mirtazapine?) but also get out the stinkiest cat food you can find and warm it and add warm water/broth to it. We need to improve her eating experience. If she isn't eating well her electrolyte levels will be off and she will be weak so fluids are a great idea. If she continues not to eat an esophageal feeding tube should be placed so we don't get into trouble with hepatic lipidosis (fatty liver disease caused by overwhelming the liver with fats broken down for energy to live when they don't eat).
Many cats, especially purebreds from a cattery type situation, carry viral upper respiratory viruses chronically. They may have a flare-up once in their life or here and there when under stress. Signs can range from sneezing, a clear nasal discharge to high fever, lethargy and eye discharge and loss of appetite. In some cases however, either due to a severe infection as a small kitten that destroyed the normal nasal anatomy or because of a chronically suppressed immune system, the symptoms linger throughout their life. These cats we call "snorters" as they will often snore or snort due to chronic infection/inflammation and destruction of their normal nasal anatomy and will have a chronic nasal discharge. The discharge is usually clear, from both sides of the nose equally and the cats don't seem otherwise sick. We almost never see a bloody discharge with these cats unless they are in very dry conditions, are hypertensive and have been sneezing a lot.
The most common cause of viral upper respiratory infections in cats is the Herpes virus so I recommend trying an amino acid supplement called L-lysine at 250mg to 500mg orally twice daily. If this infection is due to Herpes this amino acid interferes with virus replication and will shorten the infection's duration and severity during an outbreak. Good supplements to try are made by the Viralys brand which comes in a powder to add to the food or a tasty gel. You can give this supplement long term at a low level and increase it when the symptoms worsen. There is controversy about whether this really works or not but I have seen some cats improve on it, it doesn't hurt so it's worth trying.
I also recommend using a humidifier to help thin nasal secretions and keep the nasal mucosa moist, both of which help them breathe better and more comfortably.
Because her symptoms have worsened there are a few possibilities.
One is that a secondary bacterial or fungal infection has taken advantage of her damaged nose and is growing in her sinuses/nose. These tend to cause a cloudy, or green or yellow, thicker discharge and often we do see some blood due to the infection destroying normal tissue. It can be difficult to get high enough levels of antibiotics/antifungals to these areas because of the scar tissue and previous damage. And of course we must make sure to use the proper antibiotic/antifungal for the correct length of time. We may need to give medications for weeks to months to clear these infections. Rhinoscopy with cultures (both bacterial and fungal) and flushing is a great idea to look for abnormalities, gather culture samples and possibly flush out a foreign body (like a grass awn). Radiographs of her nose and sinuses are also helpful in some cases. Sometimes a CT scan or MRI of the nose is needed to find the problem area. It is possible that the infective agent is resistant to Orbax or that we are dealing with a fungal infection rather than a bacterial infection.
Another possibility is a polyp or mass in her nose that is painful and is interfering with her ability to get air through her nose. A mass will allow a secondary bacterial infection to thrive as it gives the bacteria nooks and crannies to hide in and grow and stimulates mucous production (great food for secondary invaders) as it is an irritant.
Sometimes we can see a polyp or mass when we perform rhinoscopy or radiographs of the nose but often an MRI or CT is needed. If one of these is seen I recommend a referral to a veterinary surgeon for removal. These are difficult to remove and we want to get it all on the first try.
Hopefully you will get some results back and we can chat further about her. Let me know when you get more information.