SADIE, what is wrong with you?

Get Sadie oi the Vet! It sounds like she may have something serious. Before you go, let her defecate and take a sample along with you. This way they can screen for Parvo,Giardia or Coccidia. All three of these can be common in strays and are VERY contagious. If Sadie has any evidence of blood in her stool, or is dehydrated it is even more urgent. Good luck, I hope Sadie is okay!