If your sister has just been scratched by your dog and if there is a no deep wound, she will not require a dose of Favirab.
Favirab is anti rabies immunonoglobin (antibody) which is only given in very serious wild animal bites to the face and deep wounds. It is not required if the wound is superficial or if the pet dog has been vaccinated.
I would suggest you do the following.
1) Observe the dog for 10 days. If it develops signs of rabies like change of behavior, frequent barking or biting, then consider Favirab.
2) Get the pup vaccinated if not already vaccinated.
3) Superficial Dog wounds get infected frequently .I would suggest a prophylactic dose of antibiotic Tab augmentin single dose for 7 days.
4) Apply ointment Povidone ointment on the wound and cover the wound externally with a bandage to prevent super infection of the wound.