Thanks for your query.
90% of the snakes are non-poisonous. In case of bites by non-poisonous snakes, there is minimal swelling, pain and redness
at the site of bite. But, extension of swelling to the entire limb is indeed, A CAUSE OF CONCERN.
I have no idea of the time elapsed after the snake bite
. You too are not sure the species of snake.
Hence, I STRONGLY RECOMMEND that you take your sister back to ER IMMEDIATELY, as bite by a poisonous snake cannot be ruled out and may therefore need anti-snake venom if indicated. However, the swelling over the entire limb can also be due to severe infection which has entered through the bite marks and spread all over the limb. In any case, URGENT review by ER is mandatory.
Dr. Rakesh Karanwal