The vomitus of digested liquid ( versus regurgitation of freshly chewed food), and the fact that your pet is acting reclusive, would make me lean towards the suggestion that she should be seen by your veterinarian in the morning.
Feeding table food to cats is a Russian Roulette kind of thing. Sometimes you can feed something and not notice any kind of gastrointestinal upset, and then other times, even the smallest lick of something not in the normal diet, can set your pet off in a tailspin of gastrointestinal distress!
Siamese are especially prone to food sensitivities, inflammatory bowel disease, and bouts of pancreatitis.
As vomiting and lack of appetite and decreased intake of water can quickly lead to dehydration, it is very much important that she be assessed by your vet for the need of supplemental fluids and any specific supportive therapeutic protocol.
Most cats with pancreatitis will have a fever, have painful abdomens, and have elevations in their serum Amylase, Lipase, White Blood Cell Count, and liver enzymes when we do baseline bloodwork for vomiting. In cats, bloodwork can be completely NORMAL and the cat can STILL be very, very ill and in need of immediate hospitalization.
For more info on feline Pancreatitis and vomiting, please review the following links:
On the flip side, your pet may just be experiencing a mild bout of gastritis or stomach upset that could be due to the new food item, a hairball, foreign body, or virus. Simple rest of the stomach for 12 hours, a bland diet, and antacids and stomach protectants may be all that is needed to help your pet return to feeling normal!
Having your pet examined by your vet to rule out all of the possibilities is the safest alternative for your pet!
I hope you found this information helpful and supportive. Please remember to PRESS ACCEPT so that I can be compensated for my time and professional attention to your question and your pet's specific needs. I appreciate all feedback and any type of bonus!!
Best wishes to you and your pet!!
Dr. Jodi Lynn Smith