She really needs to be seen by a vet. However, in the mean time, perhaps your can answer some questions.
--Is she spayed?
--Is she drinking normal amounts of water and urinating normal amounts?
--Any vomiting, diarrhea, coughing?
--How long has she been sick?
--Any changes you can think of?--diet, exposure to other dogs, unusual treats, etc.
--Are her gums pale?
--Is she breathing normally?
--If you press on her abdomen, does it seem uncomfortable?