It sounds like you may not be putting the syringe deep enough in her throat...there's a flap in their throat they close to keep splinters and stuff like that in their mouth while they are gnawing...they then spit it out. If you don't get the syringe past this flap rats can hold it in their mouth and drool or spit it out. Don't be surprised if they open their mouth up like they are choking, because once you remove the syringe they will be fine.