Rattlesnake venom takes up to an hour to kill a human, it was the mothers venom that did the most damage. 'Running' back to the house did more harm then anything as that would circulate the blood faster.
Ambulances carry mutliple types of anti-venom(atleast in florida) so she would have been getting treatment immediately.
If you get bit by a venomous snake your first action is to limit circulation to that part of your body. Tying your shirt above the bite area will drastically increase your survival time.