my chauaua is very sick, she is 2 years old .I recently let an older couple have her, but they had to bring her back.she would not eat or drink .they had her for about 4 days.since shes been back she has gotten worse and now she is throwing up blood and is very weak.please help i dont know what has happened to her .i tried to do the right thing by her she was getting very aggresive with my granchildren . please help