In an unspayed animal when we see liquid coming form the vaginal area that leaves a wet spot coupled with loss of appetite and lethargy we worry about what is called a pyometra. This is an infection in the uterus. When this happens it can become life threatening rather quickly and the only way to resolve this is an emergency spay. The following link provide additional information on Pyometras in cats. Link
It could also be that she has a urinary tract infection or kidney infection. In some cases when this is the problem they pass urine more frequently so it is not as concentrated as normal so it may not have a odor.
Cats unlike dogs do not stop eating unless they are ill or very stressed. When a cat stops eating this has a direct impact on their liver.
It's a good thing that you have an appointment for her today. Some things you can expect when you go in are the following.
1. Urinalysis- This will allow your vet to look for signs of infection or problems like urinary crystals.
2. X rays. Because she is not spayed your vet may want to do an x ray to see if there are any signs of fluid collection in the uterus which would indicate infection.
3. Blood work. Your vet will likely want to do blood work to look at the blood glucose levels and the kidney values.
Of course there are other common problems such as pancreatitis that can cause them to stop eating but this would not explain the wet spot unless she was just feeling to bad to get up to use the litter box.
I hope this helps give you some direction and information on what to expect when you see the vet today. Please reply back if you have additional questions and I will be happy to continue.
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