Yes but I don't think it is necessary to mix it in 3 whole liters.I'm giving her the water with the syringe though. The 2 gram for 3 liters of water? Not sure how long she hasn't been eating. She was around 3 kilos and now she feels like 2 or 1.5 kilos.
You could add only 1.5 grams to 1.5 liters...or even calculate out a smaller amount.
If she isn't getting better and doesn't start eating soon I (personally) wouldn't let her suffer much longer.