The most common cause of sneezing in a cat is viral infections, but other things such as irritants, allergies, foreign bodies and tumors can also cause sneezing. One thing to monitor is the color of the discharge that she is sneezing. Clear is OK, but if it turns yellow or greenish, or gets a bloody tinge, that is more concerning.
You didn't mention if your cat is indoor only or not or if her vaccines are up to date, but it doesn't matter so much in that even indoor cats with a current vaccine status can have a bout of viral upper respiratory infection. Older cat's are a little more at risk as their immune systems are not a resilient and may have a little more difficulty fighting off an infection. The fact that she is eating and drinking is a good sign. As long as that continues, you would be OK to monitor her for a few days. If the discharge changes color or if it goes on for longer than a week I would get her in for an exam. Another reason to get her in sooner vs later would be if she stops eating or starts acting lethargic.
The recent onset of blindness of deafness are probably not related to the sneezing unless there is a mass of some sort in her nasal cavity and/or sinuses that is expanding and impinging on her nerves. This is not common, but tumors are always a little more of a concern in older pets. It is likely that the sneezing will resolve on it's own, but if not I would definitely have it checked out.
Good luck with her and please let me know if you have any further questions.
It is possible for indoor cats to get upper respiratory viral infections. The viruses that carry them are very hearty and even if she is not exposed to other pets, the virus can travel from house to house on inanimate objects.
I agree the blindness and deafness is probably age related.
There is really not much you can do for her if it is viral to help her get over it. Her own immune system should do that. If it seems like it is not resolving however, I would have her examined to make sure there is nothing else going on. If the sneezing becomes excessive, you could try an antihistamine. Chlorpheniramine is the non-prescription one I use most often in cats. She would need between 1-2 mg and it could be repeated twice a day. There is an antiviral medicine (available as a paste in the US) called lysine, but that would need to be prescribed by a veterinarian and might be something they would consider if it was not resolving. Other than that, all you can do is to make sure she continues to eat and drink and take her in if not better soon.