First and foremost, it is very important to work out if Ada is either vomiting or in fact regurgitating. If she gobbles her food down extra quickly and 'vomits' within 5 - 10 minutes of eating, then this is most likely a regurgitation problem rather than vomiting. Likewise if she 'vomits' between half and hour to an hour after eating and the vomitus looks like undigested food, it could quite well be regurgitation again particularly if it appears tubular and compact. Regurgitation occurs either because a cat is simply eating too quickly, or because there is a functional defect with the esophagus or food pipe. If this is deterimined to defintiely be vomiting (your cat has abdominal effort and 'heaves' , plus this occurs sometime after finishing a meal), then there are quite a range of possibilites. Chronic renal failure, hyperthyroidism and diabetes can all cause chronic vomiting, particularly in older cats, and for this reason I would enourage a full blood and urine test for your girl now she is classified as 'geriatric'! Although less likely, she may have a condition known as IBD or inflammatory bowel disease or a food sensitivity, in which the immune system reacts to foreign proteins (i.e. any sort of food) in the gut, and resonds with vomiting +/- diarrhea.