Sick 2 year old, can't figure out why

My 2 year old spayed female tabby has recently fell ill. Last Thursday I noticed she'd thrown up saliva & figured it might just be a hairball. Her appetite was still normal at that point. However, every day since Thursday she's thrown up (no sign of food in her vomit) & its not like her to throw up. She started acting out of character & very mellow when shes normally bouncing off the walls. After she'd vomit she was acting uncomfortable & would go into her bed & sleep, it was clear she's under the weather. Monday I took her to the vet & they checked her out. She was running a fever & dehydrated. They decided to keep her overnight & ran some tests. The ruled out FIV and leukemia and blood work showed nothing. She threw up while there last night but her fever was down & they said she was doing well so I took her home around 5. Within an hour of getting home she already threw up twice (a lot of foam came up). The vet said it might be because she hadn't ate there so I tried feeding her Iams & Hills prescription ID which she had no interest in. I than tried giving her wet food I had on hand (Natural Balance Chicken & Green Pea LID) which she had a few licks of so I tried mixing it with white rice & she had about a teaspoon of. I than added the chicken for her bland diet & she had no interest. She also keeps spitting her meed out when I try to pill her. Any suggestions? I'm so frustrated cause I don't know what's wrong & she doesn't seem to be improving & perking back up.

She threw up twice again about 20 minutes ago. It was all bile since she hasn't ate & has no interest in eating. I rubbed some wet food on her teeth & she did lick it off but still didn't entice her to eat.

For pills you can crush them until they are powdery and mix it with wet food. If she will not eat the cat food try baby food. A last resort would be to force the mixture in her mouth using a syringe. 

Is she drinking water? 

At the vets, did they xray her stomach area? 

It could also be a viral infection. Your vet can give you meds to boost her defenses to help her recover.

I haven't seen her drink however they did IV fluids with her today so I'm not too worried. She didn't do xrays so tomorrow I think I'm going to bring her back & have them done. She did mention she thought it was a virus, I have meed but shes spitting them out when I pill her & I feel like I'm stressing her out trying to get her to swallow. I tried 4 times already cause I want to get her started on her baytril & metro to help her

After doing xrays it showed that she had a blockage in her stomach so they had to do exploratory surgery. Turns out that over the last couple of months she'd been eating my hair ties. They pulled about 25 inches worth of ties out of her. She's been home since Thursday night with me and is bouncing back very quickly. It could have been much worse but I'm glad she's feeling better and healthy again.

Oh my!!!

l'm glad you took her in for x-rays and that she's doing well.

Good vibes to both of you