Any vet has the obligation to test any animal that is suspected of having rabies, our first concern legally is supposed to be public health. If the dog had rabies and bit her, there could be very serious concequences for her.
Incidently, the incubation time for rabies can be weeks to months (typically no more than 6 months) depending on where the bite occured. It travels along nerves and not in the blood to the brain, then down nerves to the salivary glands. Within ten days of arriving in the salivary gland (and being infectious), neurolgical signs will become evident. At this time the only way to test for the disease is by examination of brain tissue (which requires death to obtain).