I am sorry to hear about this concern.
I will be out of contact for about 1.5 hours, but wanted to get you a response and some details to your answer.
At only 3 pounds, there is just no room for error because Mia can quickly dehyrate and lose body mass.
The fluids under the skin was a good first try, but if still not drinking, she really needs to get on an IV. Metronidazole is a great medication for intestinal distress and diarrhea.
She feels warm?
You can actually use any digital thermometer and take a rectal temperature. If over 103.0, that's another vote for emergency care today.
To try and encourage drinking you can also offer gatorade, pedialyte, or even adding some canne tuna juice to water to make it more palatable (make sure to change water frequently due to spoiling).
For possible stomach upset, you can also give a little 1/8 of a tablet of a Pepcid A.C. 10mg antacid. 1/8 is tough to cut, but anything a bit less than a 1/4 tablet is perfectly fine.
I wish I could do more, but definitely worth getting Mia back to a vet ASAP for better supportive care.
If I didn't fully cover everything for you, just reply and i will get back to you within the next few hours.