Could be dripping from the water bottle. Just check that and make sure it doesn't become a pattern. There are other health conditions that can cause drooling but you'll usually see the fur on under the chin soaked with it and often matted fur on the back from where the animal grooms itself. If you notice any drainage from the eyes or nose you should have her examined by a vet for respiratory infection. Otherwise just one observation isn't something to worry about.
