Hello, Gina and welcome to Just Answer.
I'm so sorry to hear that Kitty is acting ill and losing weight.
Older cats are more prone to develop various medical conditions which can cause the symptoms you're describing; for example, diabetes, hyperthyroidism, liver and kidney issues. Here is more information for you to read: Senior Cats
If she spends time outdoors, she might have gotten into a toxic substance or ingested a non-food item. Also, if she can't walk straight, this may be due to weakness or a specific condition affecting her, but it may also be a symptom of Vestibular Disease, a neurological condition that causes dizziness, nausea, and walking like a drunkard. In addition, ingestion of antifreeze can cause the same symptoms of walking like a drunkard and causes kidney failure. Vestibular DiseaseAntifreeze poisoning
Offering her the soft food and water was a great move on your part, but there is no doubt that she needs to be evaluated and treated by a vet immediately. Blood work may be necessary to make a diagnosis and then the vet will know how to treat her most appropriately.
If your regular vet doesn't have emergency hours and is closed now, bring her to the nearest ER vet center for assessment and treatment.
I hope all will be well with your Kitty!
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