I have a 9 year old granddaughter that has a slight fever of 100 and is vomiting. She cannot keep anything down, bot even the chewable medicine I have given her. Should I try a suppository medicine?

No. Take her to the doctor.

Take her to the ER or an Urgent care. I am assuming that you're her guardian? She is going to be getting really dehydrated soon and will need proper medical care. Without a lot of food, she's going to start to get diarrhea and now she's losing water and unable to replenish it. They'll take care of her.