My yorkie is sick :(?

Friday morning my 2 year old yorkie threw up yellow bile, which was not normal for her. She did it again Saturday,Sunday,Monday and Tuesday morning and was fine for the rest of the day afterwords. I took her to her vet on Tuesday afternoon and he felt her stomach and listened to her heart. He said to put her on a special diet of boiled chicken mixed with white rice and see if it settles her stomach down, hoping she might have just ate something that didn't agree with her stomach. He said if she was still sick by Thursday to bring her back in for blood tests and what not. I made her the food and she did fine on it last night and this morning and when i got home from work she had thrown up the food i gave her and had really bad diarrhea. Its later so my vet is already closed. Does anybody know what could be wrong?