Of course, we always think the worst when our elder pets start to develop symptoms. It certainly possible that something might be going on with her systemically such as issues with her kidneys or liver or possibly even cancer, unfortunately.
However, it's also possible that she may have something such as a viral or bacterial infection or even late onset Inflammatory Bowel Disease which might account for her symptoms.
I probably wouldn't be too overly concerned about the bile that she's vomiting if she's not eating. This may simply reflect acid buildup in her stomach because it's empty. Over the counter Pepcid AC (Famotidine) may help to reduce this sort of nausea. The dose would be 1/4th mg per pound of body weight twice a day.
You might also consider taking her temperature if you have a thermometer; if it's elevated, then this may explain her behavior. Normal is between 100 and 102.5. Of course, then we'd have to wonder why she's running a fever and there are a number of possible explanations which range from a bacterial/viral infection to auto-immune diseases to tick diseases to cancer, etc.
Since blood work hasn't been done recently, this would be my first suggestion if a thorough physical exam doesn't pinpoint any issues. Then, depending on the results, you'll know how to proceed.
I wouldn't automatically assume the worst but I'd be prepared for it, given her age.
I hope this helps. Deb