I am sorry that you are having this problem with Izzie. In response to your question, the pacing, restlessness, and shaking are symptoms of being in pain. The fact that she is vomiting I would assume the problem is within the abdomen. It will be difficult for me to determine the exact underlying cause without a hands-on examination and some testing, I am sorry. But, common causes are pancreatitis, dietary indiscretion, ingestion of a foreign body, infections, etc. to name a few causes. To determine the exact underlying cause she will need a hands-on examination by a veterinarian, blood work and possibly x-rays as an initial screening test. Treatment will be based on exam and test results. If you have access to ER vet I would have her checked tonight to rule out pancreatitis. I realize that this answer may not be entirely to your liking, and I regret being the bearer of information that you really don’t want to hear. But it would be unfair to you and unprofessional of me were I to provide you with anything less than truthful and honest information. I hope you understand. If you do not have access to ER vet this is what you can do until she is seen by your family veterinarian:
1- Do not give things like Pepto Bismol or Imodium. Start her on Pepcid AC (famotidine) 10mg 1/4 tablet every 12 hours. You can buy Pepcid AC over the counter in any pharmacy.
2- No food or water for 8-12 hours. Need to give her gastrointestinal tract time to rest.
3- After 8-12 hours offer a small amount of water. Wait half hour, if no vomiting, she can have water. Leave her without food for 16-20 hours then offer a small amount of rice (50%) and boiled boneless chicken or ground beef (50%) 4-6 times a day. Keep on this diet for several days then wean into regular diet.
4- Follow up with your family veterinarian for a hands on examination in the morning. If cost is a concerned look into your local ASPCA or Shelter where they often offer veterinary services at a lower cost.
My goal is to provide you with excellent service - I hope I've provided the information you were seeking, if you feel you have received anything less, please reply back as I am happy to address follow-up questions. Kindly rate me when you are done.