Ketones are best treated at the vet because they can put her on IV fluids which help flush them out. She may have to spend a day or two at your regular vet. For now, if you are home testing, and are able to syringe feed, you do want to give her insulin, but what dose depends on what she's been taking. You may have to mix karo or honey into the food you are feeding to keep her numbers up. You should test the blood sugar frequently.
For the vet tomorrow, ask about the following things:
1. Anti nausea med like cerinia or ondansetron
2. Blood test for potassium and a supplement if she's low (low potassium is common with ketones and can cause constipation and heart issues)
3. SubQ or IV fluids. If she doesn't stay at the vet ask if they can show you how to do the subQ fluids at home.
4. High cal food - Iams max cal, royal canin recovery, or whatever high cal critical care food they have
5. Supplies for syringe feeding if you don't have them
From the grocery store or pharmacy pick up some ketone urine test strips for home testing. You should home test a couple times a day.
Cats develop ketones because of lack of insulin, lack of food, or both. Infection raise insulin needs, and is often the trigger.