Hi & Welcome.
I can understand your concern for your beloved mother.
Since, at the time of bite your dog was not vaccinated so there's a possibility of being infected with rabies.
Dogs uniformly begin to sicken and die within 10 days of spread of
rabies virus from the CNS to the salivary glands. That's why a healthy domestic dog that bites a person should be confined and observed for 10 days.
Dogs that exhibit any sign of illness should be evaluated by a veterinarian and reported to the local health department. If your dog does develop any signs of illness, it should be euthanised and its head shipped under refrigeration to a laboratory certified to perform rabies testing (most often a public health laboratory).
If your dog remains healthy for the full 10 days, then it did not have rabies virus in its saliva at the time of exposure.
Besides, your mother should be given 4 doses (injections) of anti
rabies vaccine on day 0, 3, 7, & 14. If the dog remains healthy after 10 days, the fourth dose of 14 days need not be given.
Hope this answers your query.